深入理解 BigDecimal
.output_wrapper pre code { font-family: Consolas, Inconsolata, Courier, monospace; display: block !important; white-space: pre !important; word-wrap: normal !important; word-break: normal !important; overflow: auto !important }
.output_wrapper a:hover { text-decoration: underline; color: rgba(0, 96, 100, 1) }
.output_wrapper figcaption { margin-top: 10px; text-align: center; color: rgba(153, 153, 153, 1); font-size: 0.7em }
.output_wrapper pre code .linenum { padding-right: 20px; word-spacing: 0 }
.task-list-list { list-style-type: none }
.task-list-list.checked { color: rgba(62, 62, 62, 1) }
.task-list-list.uncheck { color: rgba(191, 193, 191, 1) }
.task-list-list .icon_uncheck, .task-list-list .icon_check { display: inline-block; vertical-align: middle; margin-right: 10px }
.task-list-list .icon_check::before { content: “√”; border: 2px solid rgba(62, 62, 62, 1); color: rgba(255, 0, 0, 1) }
.task-list-list .icon_uncheck::before { content: “x”; border: 2px solid rgba(191, 193, 191, 1); color: rgba(191, 193, 191, 1) }
.task-list-list .icon_check::before, .task-list-list .icon_uncheck::before { padding: 2px 8px 2px 5px; border-radius: 5px }
@font-face { font-family: KaTeX_AMS; src: url(“fonts/KaTeX_AMS-Regular.woff2”) format(“woff2”), url(“fonts/KaTeX_AMS-Regular.woff”) format(“woff”), url(“fonts/KaTeX_AMS-Regular.ttf”) format(“truetype”); font-weight: normal; font-style: normal }
@font-face { font-family: KaTeX_Caligraphic; src: url(“fonts/KaTeX_Caligraphic-Bold.woff2”) format(“woff2”), url(“fonts/KaTeX_Caligraphic-Bold.woff”) format(“woff”), url(“fonts/KaTeX_Caligraphic-Bold.ttf”) format(“truetype”); font-weight: bold; font-style: normal }
@font-face { font-family: KaTeX_Caligraphic; src: url(“fonts/KaTeX_Caligraphic-Regular.woff2”) format(“woff2”), url(“fonts/KaTeX_Caligraphic-Regular.woff”) format(“woff”), url(“fonts/KaTeX_Caligraphic-Regular.ttf”) format(“truetype”); font-weight: normal; font-style: normal }
@font-face { font-family: KaTeX_Fraktur; src: url(“fonts/KaTeX_Fraktur-Bold.woff2”) format(“woff2”), url(“fonts/KaTeX_Fraktur-Bold.woff”) format(“woff”), url(“fonts/KaTeX_Fraktur-Bold.ttf”) format(“truetype”); font-weight: bold; font-style: normal }
@font-face { font-family: KaTeX_Fraktur; src: url(“fonts/KaTeX_Fraktur-Regular.woff2”) format(“woff2”), url(“fonts/KaTeX_Fraktur-Regular.woff”) format(“woff”), url(“fonts/KaTeX_Fraktur-Regular.ttf”) format(“truetype”); font-weight: normal; font-style: normal }
@font-face { font-family: KaTeX_Main; src: url(“fonts/KaTeX_Main-Bold.woff2”) format(“woff2”), url(“fonts/KaTeX_Main-Bold.woff”) format(“woff”), url(“fonts/KaTeX_Main-Bold.ttf”) format(“truetype”); font-weight: bold; font-style: normal }
@font-face { font-family: KaTeX_Main; src: url(“fonts/KaTeX_Main-BoldItalic.woff2”) format(“woff2”), url(“fonts/KaTeX_Main-BoldItalic.woff”) format(“woff”), url(“fonts/KaTeX_Main-BoldItalic.ttf”) format(“truetype”); font-weight: bold; font-style: italic }
@font-face { font-family: KaTeX_Main; src: url(“fonts/KaTeX_Main-Italic.woff2”) format(“woff2”), url(“fonts/KaTeX_Main-Italic.woff”) format(“woff”), url(“fonts/KaTeX_Main-Italic.ttf”) format(“truetype”); font-weight: normal; font-style: italic }
@font-face { font-family: KaTeX_Main; src: url(“fonts/KaTeX_Main-Regular.woff2”) format(“woff2”), url(“fonts/KaTeX_Main-Regular.woff”) format(“woff”), url(“fonts/KaTeX_Main-Regular.ttf”) format(“truetype”); font-weight: normal; font-style: normal }
@font-face { font-family: KaTeX_Math; src: url(“fonts/KaTeX_Math-BoldItalic.woff2”) format(“woff2”), url(“fonts/KaTeX_Math-BoldItalic.woff”) format(“woff”), url(“fonts/KaTeX_Math-BoldItalic.ttf”) format(“truetype”); font-weight: bold; font-style: italic }
@font-face { font-family: KaTeX_Math; src: url(“fonts/KaTeX_Math-Italic.woff2”) format(“woff2”), url(“fonts/KaTeX_Math-Italic.woff”) format(“woff”), url(“fonts/KaTeX_Math-Italic.ttf”) format(“truetype”); font-weight: normal; font-style: italic }
@font-face { font-family: KaTeX_SansSerif; src: url(“fonts/KaTeX_SansSerif-Bold.woff2”) format(“woff2”), url(“fonts/KaTeX_SansSerif-Bold.woff”) format(“woff”), url(“fonts/KaTeX_SansSerif-Bold.ttf”) format(“truetype”); font-weight: bold; font-style: normal }
@font-face { font-family: KaTeX_SansSerif; src: url(“fonts/KaTeX_SansSerif-Italic.woff2”) format(“woff2”), url(“fonts/KaTeX_SansSerif-Italic.woff”) format(“woff”), url(“fonts/KaTeX_SansSerif-Italic.ttf”) format(“truetype”); font-weight: normal; font-style: italic }
@font-face { font-family: KaTeX_SansSerif; src: url(“fonts/KaTeX_SansSerif-Regular.woff2”) format(“woff2”), url(“fonts/KaTeX_SansSerif-Regular.woff”) format(“woff”), url(“fonts/KaTeX_SansSerif-Regular.ttf”) format(“truetype”); font-weight: normal; font-style: normal }
@font-face { font-family: KaTeX_Script; src: url(“fonts/KaTeX_Script-Regular.woff2”) format(“woff2”), url(“fonts/KaTeX_Script-Regular.woff”) format(“woff”), url(“fonts/KaTeX_Script-Regular.ttf”) format(“truetype”); font-weight: normal; font-style: normal }
@font-face { font-family: KaTeX_Size1; src: url(“fonts/KaTeX_Size1-Regular.woff2”) format(“woff2”), url(“fonts/KaTeX_Size1-Regular.woff”) format(“woff”), url(“fonts/KaTeX_Size1-Regular.ttf”) format(“truetype”); font-weight: normal; font-style: normal }
@font-face { font-family: KaTeX_Size2; src: url(“fonts/KaTeX_Size2-Regular.woff2”) format(“woff2”), url(“fonts/KaTeX_Size2-Regular.woff”) format(“woff”), url(“fonts/KaTeX_Size2-Regular.ttf”) format(“truetype”); font-weight: normal; font-style: normal }
@font-face { font-family: KaTeX_Size3; src: url(“fonts/KaTeX_Size3-Regular.woff2”) format(“woff2”), url(“fonts/KaTeX_Size3-Regular.woff”) format(“woff”), url(“fonts/KaTeX_Size3-Regular.ttf”) format(“truetype”); font-weight: normal; font-style: normal }
@font-face { font-family: KaTeX_Size4; src: url(“fonts/KaTeX_Size4-Regular.woff2”) format(“woff2”), url(“fonts/KaTeX_Size4-Regular.woff”) format(“woff”), url(“fonts/KaTeX_Size4-Regular.ttf”) format(“truetype”); font-weight: normal; font-style: normal }
@font-face { font-family: KaTeX_Typewriter; src: url(“fonts/KaTeX_Typewriter-Regular.woff2”) format(“woff2”), url(“fonts/KaTeX_Typewriter-Regular.woff”) format(“woff”), url(“fonts/KaTeX_Typewriter-Regular.ttf”) format(“truetype”); font-weight: normal; font-style: normal }
@media screen { .katex .mtable .vertical-separator { min-width: 1px } .katex .mfrac .frac-line, .katex .overline .overline-line, .katex .underline .underline-line, .katex .hline, .katex .hdashline, .katex .rule { min-height: 1px } }
.katex-display { display: block; margin: 1em 0; text-align: center }
.katex-display>.katex { display: block; text-align: center; white-space: nowrap }
.katex-display>.katex>.katex-html { display: block }
.katex-display>.katex>.katex-html>.tag { position: absolute; right: 0 }
.katex { font: 1.21em / 1.2 KaTeX_Main, “Times New Roman”, serif; text-indent: 0; text-rendering: auto }
.katex * { }
.katex .katex-mathml { position: absolute; clip: rect(1px, 1px, 1px, 1px); padding: 0; border: 0; height: 1px; width: 1px; overflow: hidden }
.katex .katex-html { }
.katex .katex-html>.newline { display: block }
.katex .base { position: relative; display: inline-block; white-space: nowrap; width: min-content }
.katex .strut { display: inline-block }
.katex .textbf { font-weight: bold }
.katex .textit { font-style: italic }
.katex .textrm { font-family: KaTeX_Main }
.katex .textsf { font-family: KaTeX_SansSerif }
.katex .texttt { font-family: KaTeX_Typewriter }
.katex .mathit { font-family: KaTeX_Math; font-style: italic }
.katex .mathrm { font-style: normal }
.katex .mathbf { font-family: KaTeX_Main; font-weight: bold }
.katex .boldsymbol { font-family: KaTeX_Math; font-weight: bold; font-style: italic }
.katex .amsrm { font-family: KaTeX_AMS }
.katex .mathbb, .katex .textbb { font-family: KaTeX_AMS }
.katex .mathcal { font-family: KaTeX_Caligraphic }
.katex .mathfrak, .katex .textfrak { font-family: KaTeX_Fraktur }
.katex .mathtt { font-family: KaTeX_Typewriter }
.katex .mathscr, .katex .textscr { font-family: KaTeX_Script }
.katex .mathsf, .katex .textsf { font-family: KaTeX_SansSerif }
.katex .mainit { font-family: KaTeX_Main; font-style: italic }
.katex .mainrm { font-family: KaTeX_Main; font-style: normal }
.katex .vlist-t { display: inline-table; table-layout: fixed }
.katex .vlist-r { display: table-row }
.katex .vlist { display: table-cell; vertical-align: bottom; position: relative }
.katex .vlist>span { display: block; height: 0; position: relative }
.katex .vlist>span>span { display: inline-block }
.katex .vlist>span>.pstrut { overflow: hidden; width: 0 }
.katex .vlist-t2 { margin-right: -2px }
.katex .vlist-s { display: table-cell; vertical-align: bottom; font-size: 1px; width: 2px; min-width: 2px }
.katex .msupsub { text-align: left }
.katex .mfrac>span>span { text-align: center }
.katex .mfrac .frac-line { display: inline-block; width: 100%; border-bottom-style: solid }
.katex .mspace { display: inline-block }
.katex .llap, .katex .rlap, .katex .clap { width: 0; position: relative }
.katex .llap>.inner, .katex .rlap>.inner, .katex .clap>.inner { position: absolute }
.katex .llap>.fix, .katex .rlap>.fix, .katex .clap>.fix { display: inline-block }
.katex .llap>.inner { right: 0 }
.katex .rlap>.inner, .katex .clap>.inner { left: 0 }
.katex .clap>.inner>span { margin-left: -50%; margin-right: 50% }
.katex .rule { display: inline-block; border: 0 solid; position: relative }
.katex .overline .overline-line, .katex .underline .underline-line, .katex .hline { display: inline-block; width: 100%; border-bottom-style: solid }
.katex .hdashline { display: inline-block; width: 100%; border-bottom-style: dashed }
.katex .sqrt>.root { margin-left: 0.277778em; margin-right: -0.555556em }
.katex .sizing, .katex .fontsize-ensurer { display: inline-block }
.katex .sizing.reset-size1.size1, .katex .fontsize-ensurer.reset-size1.size1 { font-size: 1em }
.katex .sizing.reset-size1.size2, .katex .fontsize-ensurer.reset-size1.size2 { font-size: 1.2em }
.katex .sizing.reset-size1.size3, .katex .fontsize-ensurer.reset-size1.size3 { font-size: 1.4em }
.katex .sizing.reset-size1.size4, .katex .fontsize-ensurer.reset-size1.size4 { font-size: 1.6em }
.katex .sizing.reset-size1.size5, .katex .fontsize-ensurer.reset-size1.size5 { font-size: 1.8em }
.katex .sizing.reset-size1.size6, .katex .fontsize-ensurer.reset-size1.size6 { font-size: 2em }
.katex .sizing.reset-size1.size7, .katex .fontsize-ensurer.reset-size1.size7 { font-size: 2.4em }
.katex .sizing.reset-size1.size8, .katex .fontsize-ensurer.reset-size1.size8 { font-size: 2.88em }
.katex .sizing.reset-size1.size9, .katex .fontsize-ensurer.reset-size1.size9 { font-size: 3.456em }
.katex .sizing.reset-size1.size10, .katex .fontsize-ensurer.reset-size1.size10 { font-size: 4.148em }
.katex .sizing.reset-size1.size11, .katex .fontsize-ensurer.reset-size1.size11 { font-size: 4.976em }
.katex .sizing.reset-size2.size1, .katex .fontsize-ensurer.reset-size2.size1 { font-size: 0.833333em }
.katex .sizing.reset-size2.size2, .katex .fontsize-ensurer.reset-size2.size2 { font-size: 1em }
.katex .sizing.reset-size2.size3, .katex .fontsize-ensurer.reset-size2.size3 { font-size: 1.16667em }
.katex .sizing.reset-size2.size4, .katex .fontsize-ensurer.reset-size2.size4 { font-size: 1.33333em }
.katex .sizing.reset-size2.size5, .katex .fontsize-ensurer.reset-size2.size5 { font-size: 1.5em }
.katex .sizing.reset-size2.size6, .katex .fontsize-ensurer.reset-size2.size6 { font-size: 1.66667em }
.katex .sizing.reset-size2.size7, .katex .fontsize-ensurer.reset-size2.size7 { font-size: 2em }
.katex .sizing.reset-size2.size8, .katex .fontsize-ensurer.reset-size2.size8 { font-size: 2.4em }
.katex .sizing.reset-size2.size9, .katex .fontsize-ensurer.reset-size2.size9 { font-size: 2.88em }
.katex .sizing.reset-size2.size10, .katex .fontsize-ensurer.reset-size2.size10 { font-size: 3.45667em }
.katex .sizing.reset-size2.size11, .katex .fontsize-ensurer.reset-size2.size11 { font-size: 4.14667em }
.katex .sizing.reset-size3.size1, .katex .fontsize-ensurer.reset-size3.size1 { font-size: 0.714286em }
.katex .sizing.reset-size3.size2, .katex .fontsize-ensurer.reset-size3.size2 { font-size: 0.857143em }
.katex .sizing.reset-size3.size3, .katex .fontsize-ensurer.reset-size3.size3 { font-size: 1em }
.katex .sizing.reset-size3.size4, .katex .fontsize-ensurer.reset-size3.size4 { font-size: 1.14286em }
.katex .sizing.reset-size3.size5, .katex .fontsize-ensurer.reset-size3.size5 { font-size: 1.28571em }
.katex .sizing.reset-size3.size6, .katex .fontsize-ensurer.reset-size3.size6 { font-size: 1.42857em }
.katex .sizing.reset-size3.size7, .katex .fontsize-ensurer.reset-size3.size7 { font-size: 1.71429em }
.katex .sizing.reset-size3.size8, .katex .fontsize-ensurer.reset-size3.size8 { font-size: 2.05714em }
.katex .sizing.reset-size3.size9, .katex .fontsize-ensurer.reset-size3.size9 { font-size: 2.46857em }
.katex .sizing.reset-size3.size10, .katex .fontsize-ensurer.reset-size3.size10 { font-size: 2.96286em }
.katex .sizing.reset-size3.size11, .katex .fontsize-ensurer.reset-size3.size11 { font-size: 3.55429em }
.katex .sizing.reset-size4.size1, .katex .fontsize-ensurer.reset-size4.size1 { font-size: 0.625em }
.katex .sizing.reset-size4.size2, .katex .fontsize-ensurer.reset-size4.size2 { font-size: 0.75em }
.katex .sizing.reset-size4.size3, .katex .fontsize-ensurer.reset-size4.size3 { font-size: 0.875em }
.katex .sizing.reset-size4.size4, .katex .fontsize-ensurer.reset-size4.size4 { font-size: 1em }
.katex .sizing.reset-size4.size5, .katex .fontsize-ensurer.reset-size4.size5 { font-size: 1.125em }
.katex .sizing.reset-size4.size6, .katex .fontsize-ensurer.reset-size4.size6 { font-size: 1.25em }
.katex .sizing.reset-size4.size7, .katex .fontsize-ensurer.reset-size4.size7 { font-size: 1.5em }
.katex .sizing.reset-size4.size8, .katex .fontsize-ensurer.reset-size4.size8 { font-size: 1.8em }
.katex .sizing.reset-size4.size9, .katex .fontsize-ensurer.reset-size4.size9 { font-size: 2.16em }
.katex .sizing.reset-size4.size10, .katex .fontsize-ensurer.reset-size4.size10 { font-size: 2.5925em }
.katex .sizing.reset-size4.size11, .katex .fontsize-ensurer.reset-size4.size11 { font-size: 3.11em }
.katex .sizing.reset-size5.size1, .katex .fontsize-ensurer.reset-size5.size1 { font-size: 0.555556em }
.katex .sizing.reset-size5.size2, .katex .fontsize-ensurer.reset-size5.size2 { font-size: 0.666667em }
.katex .sizing.reset-size5.size3, .katex .fontsize-ensurer.reset-size5.size3 { font-size: 0.777778em }
.katex .sizing.reset-size5.size4, .katex .fontsize-ensurer.reset-size5.size4 { font-size: 0.888889em }
.katex .sizing.reset-size5.size5, .katex .fontsize-ensurer.reset-size5.size5 { font-size: 1em }
.katex .sizing.reset-size5.size6, .katex .fontsize-ensurer.reset-size5.size6 { font-size: 1.11111em }
.katex .sizing.reset-size5.size7, .katex .fontsize-ensurer.reset-size5.size7 { font-size: 1.33333em }
.katex .sizing.reset-size5.size8, .katex .fontsize-ensurer.reset-size5.size8 { font-size: 1.6em }
.katex .sizing.reset-size5.size9, .katex .fontsize-ensurer.reset-size5.size9 { font-size: 1.92em }
.katex .sizing.reset-size5.size10, .katex .fontsize-ensurer.reset-size5.size10 { font-size: 2.30444em }
.katex .sizing.reset-size5.size11, .katex .fontsize-ensurer.reset-size5.size11 { font-size: 2.76444em }
.katex .sizing.reset-size6.size1, .katex .fontsize-ensurer.reset-size6.size1 { font-size: 0.5em }
.katex .sizing.reset-size6.size2, .katex .fontsize-ensurer.reset-size6.size2 { font-size: 0.6em }
.katex .sizing.reset-size6.size3, .katex .fontsize-ensurer.reset-size6.size3 { font-size: 0.7em }
.katex .sizing.reset-size6.size4, .katex .fontsize-ensurer.reset-size6.size4 { font-size: 0.8em }
.katex .sizing.reset-size6.size5, .katex .fontsize-ensurer.reset-size6.size5 { font-size: 0.9em }
.katex .sizing.reset-size6.size6, .katex .fontsize-ensurer.reset-size6.size6 { font-size: 1em }
.katex .sizing.reset-size6.size7, .katex .fontsize-ensurer.reset-size6.size7 { font-size: 1.2em }
.katex .sizing.reset-size6.size8, .katex .fontsize-ensurer.reset-size6.size8 { font-size: 1.44em }
.katex .sizing.reset-size6.size9, .katex .fontsize-ensurer.reset-size6.size9 { font-size: 1.728em }
.katex .sizing.reset-size6.size10, .katex .fontsize-ensurer.reset-size6.size10 { font-size: 2.074em }
.katex .sizing.reset-size6.size11, .katex .fontsize-ensurer.reset-size6.size11 { font-size: 2.488em }
.katex .sizing.reset-size7.size1, .katex .fontsize-ensurer.reset-size7.size1 { font-size: 0.416667em }
.katex .sizing.reset-size7.size2, .katex .fontsize-ensurer.reset-size7.size2 { font-size: 0.5em }
.katex .sizing.reset-size7.size3, .katex .fontsize-ensurer.reset-size7.size3 { font-size: 0.583333em }
.katex .sizing.reset-size7.size4, .katex .fontsize-ensurer.reset-size7.size4 { font-size: 0.666667em }
.katex .sizing.reset-size7.size5, .katex .fontsize-ensurer.reset-size7.size5 { font-size: 0.75em }
.katex .sizing.reset-size7.size6, .katex .fontsize-ensurer.reset-size7.size6 { font-size: 0.833333em }
.katex .sizing.reset-size7.size7, .katex .fontsize-ensurer.reset-size7.size7 { font-size: 1em }
.katex .sizing.reset-size7.size8, .katex .fontsize-ensurer.reset-size7.size8 { font-size: 1.2em }
.katex .sizing.reset-size7.size9, .katex .fontsize-ensurer.reset-size7.size9 { font-size: 1.44em }
.katex .sizing.reset-size7.size10, .katex .fontsize-ensurer.reset-size7.size10 { font-size: 1.72833em }
.katex .sizing.reset-size7.size11, .katex .fontsize-ensurer.reset-size7.size11 { font-size: 2.07333em }
.katex .sizing.reset-size8.size1, .katex .fontsize-ensurer.reset-size8.size1 { font-size: 0.347222em }
.katex .sizing.reset-size8.size2, .katex .fontsize-ensurer.reset-size8.size2 { font-size: 0.416667em }
.katex .sizing.reset-size8.size3, .katex .fontsize-ensurer.reset-size8.size3 { font-size: 0.486111em }
.katex .sizing.reset-size8.size4, .katex .fontsize-ensurer.reset-size8.size4 { font-size: 0.555556em }
.katex .sizing.reset-size8.size5, .katex .fontsize-ensurer.reset-size8.size5 { font-size: 0.625em }
.katex .sizing.reset-size8.size6, .katex .fontsize-ensurer.reset-size8.size6 { font-size: 0.694444em }
.katex .sizing.reset-size8.size7, .katex .fontsize-ensurer.reset-size8.size7 { font-size: 0.833333em }
.katex .sizing.reset-size8.size8, .katex .fontsize-ensurer.reset-size8.size8 { font-size: 1em }
.katex .sizing.reset-size8.size9, .katex .fontsize-ensurer.reset-size8.size9 { font-size: 1.2em }
.katex .sizing.reset-size8.size10, .katex .fontsize-ensurer.reset-size8.size10 { font-size: 1.44028em }
.katex .sizing.reset-size8.size11, .katex .fontsize-ensurer.reset-size8.size11 { font-size: 1.72778em }
.katex .sizing.reset-size9.size1, .katex .fontsize-ensurer.reset-size9.size1 { font-size: 0.289352em }
.katex .sizing.reset-size9.size2, .katex .fontsize-ensurer.reset-size9.size2 { font-size: 0.347222em }
.katex .sizing.reset-size9.size3, .katex .fontsize-ensurer.reset-size9.size3 { font-size: 0.405093em }
.katex .sizing.reset-size9.size4, .katex .fontsize-ensurer.reset-size9.size4 { font-size: 0.462963em }
.katex .sizing.reset-size9.size5, .katex .fontsize-ensurer.reset-size9.size5 { font-size: 0.520833em }
.katex .sizing.reset-size9.size6, .katex .fontsize-ensurer.reset-size9.size6 { font-size: 0.578704em }
.katex .sizing.reset-size9.size7, .katex .fontsize-ensurer.reset-size9.size7 { font-size: 0.694444em }
.katex .sizing.reset-size9.size8, .katex .fontsize-ensurer.reset-size9.size8 { font-size: 0.833333em }
.katex .sizing.reset-size9.size9, .katex .fontsize-ensurer.reset-size9.size9 { font-size: 1em }
.katex .sizing.reset-size9.size10, .katex .fontsize-ensurer.reset-size9.size10 { font-size: 1.20023em }
.katex .sizing.reset-size9.size11, .katex .fontsize-ensurer.reset-size9.size11 { font-size: 1.43981em }
.katex .sizing.reset-size10.size1, .katex .fontsize-ensurer.reset-size10.size1 { font-size: 0.24108em }
.katex .sizing.reset-size10.size2, .katex .fontsize-ensurer.reset-size10.size2 { font-size: 0.289296em }
.katex .sizing.reset-size10.size3, .katex .fontsize-ensurer.reset-size10.size3 { font-size: 0.337512em }
.katex .sizing.reset-size10.size4, .katex .fontsize-ensurer.reset-size10.size4 { font-size: 0.385728em }
.katex .sizing.reset-size10.size5, .katex .fontsize-ensurer.reset-size10.size5 { font-size: 0.433944em }
.katex .sizing.reset-size10.size6, .katex .fontsize-ensurer.reset-size10.size6 { font-size: 0.48216em }
.katex .sizing.reset-size10.size7, .katex .fontsize-ensurer.reset-size10.size7 { font-size: 0.578592em }
.katex .sizing.reset-size10.size8, .katex .fontsize-ensurer.reset-size10.size8 { font-size: 0.694311em }
.katex .sizing.reset-size10.size9, .katex .fontsize-ensurer.reset-size10.size9 { font-size: 0.833173em }
.katex .sizing.reset-size10.size10, .katex .fontsize-ensurer.reset-size10.size10 { font-size: 1em }
.katex .sizing.reset-size10.size11, .katex .fontsize-ensurer.reset-size10.size11 { font-size: 1.19961em }
.katex .sizing.reset-size11.size1, .katex .fontsize-ensurer.reset-size11.size1 { font-size: 0.200965em }
.katex .sizing.reset-size11.size2, .katex .fontsize-ensurer.reset-size11.size2 { font-size: 0.241158em }
.katex .sizing.reset-size11.size3, .katex .fontsize-ensurer.reset-size11.size3 { font-size: 0.28135em }
.katex .sizing.reset-size11.size4, .katex .fontsize-ensurer.reset-size11.size4 { font-size: 0.321543em }
.katex .sizing.reset-size11.size5, .katex .fontsize-ensurer.reset-size11.size5 { font-size: 0.361736em }
.katex .sizing.reset-size11.size6, .katex .fontsize-ensurer.reset-size11.size6 { font-size: 0.401929em }
.katex .sizing.reset-size11.size7, .katex .fontsize-ensurer.reset-size11.size7 { font-size: 0.482315em }
.katex .sizing.reset-size11.size8, .katex .fontsize-ensurer.reset-size11.size8 { font-size: 0.578778em }
.katex .sizing.reset-size11.size9, .katex .fontsize-ensurer.reset-size11.size9 { font-size: 0.694534em }
.katex .sizing.reset-size11.size10, .katex .fontsize-ensurer.reset-size11.size10 { font-size: 0.833601em }
.katex .sizing.reset-size11.size11, .katex .fontsize-ensurer.reset-size11.size11 { font-size: 1em }
.katex .delimsizing.size1 { font-family: KaTeX_Size1 }
.katex .delimsizing.size2 { font-family: KaTeX_Size2 }
.katex .delimsizing.size3 { font-family: KaTeX_Size3 }
.katex .delimsizing.size4 { font-family: KaTeX_Size4 }
.katex .delimsizing.mult .delim-size1>span { font-family: KaTeX_Size1 }
.katex .delimsizing.mult .delim-size4>span { font-family: KaTeX_Size4 }
.katex .nulldelimiter { display: inline-block; width: 0.12em }
.katex .delimcenter { position: relative }
.katex .op-symbol { position: relative }
.katex .op-symbol.small-op { font-family: KaTeX_Size1 }
.katex .op-symbol.large-op { font-family: KaTeX_Size2 }
.katex .op-limits>.vlist-t { text-align: center }
.katex .accent>.vlist-t { text-align: center }
.katex .accent .accent-body:not(.accent-full) { width: 0 }
.katex .accent .accent-body { position: relative }
.katex .overlay { display: block }
.katex .mtable .vertical-separator { display: inline-block; margin: 0 -0.025em; border-right: 0.05em solid }
.katex .mtable .vs-dashed { border-right: 0.05em dashed }
.katex .mtable .arraycolsep { display: inline-block }
.katex .mtable .col-align-c>.vlist-t { text-align: center }
.katex .mtable .col-align-l>.vlist-t { text-align: left }
.katex .mtable .col-align-r>.vlist-t { text-align: right }
.katex .svg-align { text-align: left }
.katex svg, .screenShotTempCanvas { display: block; position: absolute; width: 100%; height: inherit; fill: currentColor; stroke: currentColor; fill-rule: nonzero; fill-opacity: 1; stroke-width: 1; stroke-linecap: butt; stroke-linejoin: miter; stroke-miterlimit: 4; stroke-dasharray: none; stroke-dashoffset: 0; stroke-opacity: 1 }
.katex svg path { stroke: none }
.katex .stretchy { width: 100%; display: block; position: relative; overflow: hidden }
.katex .stretchy::before, .katex .stretchy::after { content: “” }
.katex .hide-tail { width: 100%; position: relative; overflow: hidden }
.katex .halfarrow-left { position: absolute; left: 0; width: 50.2%; overflow: hidden }
.katex .halfarrow-right { position: absolute; right: 0; width: 50.2%; overflow: hidden }
.katex .brace-left { position: absolute; left: 0; width: 25.1%; overflow: hidden }
.katex .brace-center { position: absolute; left: 25%; width: 50%; overflow: hidden }
.katex .brace-right { position: absolute; right: 0; width: 25.1%; overflow: hidden }
.katex .x-arrow-pad { padding: 0 0.5em }
.katex .x-arrow, .katex .mover, .katex .munder { text-align: center }
.katex .boxpad { padding: 0 0.3em }
.katex .fbox { box-sizing: border-box; border: 0.04em solid rgba(0, 0, 0, 1) }
.katex .fcolorbox { box-sizing: border-box; border: 0.04em solid }
.katex .cancel-pad { padding: 0 0.2em }
.katex .cancel-lap { margin-left: -0.2em; margin-right: -0.2em }
.katex .sout { border-bottom-style: solid; border-bottom-width: 0.08em }
.output_wrapper pre code { }
.output_wrapper .hljs { color: rgba(169, 183, 198, 1); background: rgba(40, 43, 46, 1); display: block; overflow-x: auto; padding: 0.5em }
.output_wrapper .hljs-params { color: rgba(255, 152, 35, 1) }
.output_wrapper .hljs-number, .output_wrapper .hljs-literal, .output_wrapper .hljs-symbol, .output_wrapper .hljs-bullet { color: rgba(174, 135, 250, 1) }
.output_wrapper .hljs-function, .output_wrapper .hljs-built_in, .output_wrapper .hljs-name, .output_wrapper .hljs-keyword, .output_wrapper .hljs-selector-tag, .output_wrapper .hljs-deletion { color: rgba(248, 35, 117, 1) }
.output_wrapper .hljs-variable, .output_wrapper .hljs-template-variable, .output_wrapper .hljs-link { color: rgba(98, 151, 85, 1) }
.output_wrapper .hljs-comment, .output_wrapper .hljs-quote { color: rgba(128, 128, 128, 1) }
.output_wrapper .hljs-meta { color: rgba(91, 218, 237, 1) }
.output_wrapper .hljs-string, .output_wrapper .hljs-attribute, .output_wrapper .hljs-addition { color: rgba(238, 220, 112, 1) }
.output_wrapper .hljs-attr, .output_wrapper .hljs-section, .output_wrapper .hljs-title, .output_wrapper .hljs-type { color: rgba(165, 218, 45, 1) }
.output_wrapper .hljs-selector-class { color: rgba(165, 218, 45, 1) }
.output_wrapper .hljs-emphasis { font-style: italic }
.output_wrapper .hljs-strong { font-weight: bold }
.output_wrapper pre code { line-height: 18px; font-size: 14px; font-weight: normal; word-spacing: 0; letter-spacing: 0 }
.output_wrapper { font-size: 16px; color: rgba(62, 62, 62, 1); line-height: 1.6; word-spacing: 0; letter-spacing: 1px; font-family: “Helvetica Neue”, Helvetica, “Hiragino Sans GB”, “Microsoft YaHei”, Arial, sans-serif }
.output_wrapper * { font-size: inherit; color: inherit; line-height: inherit; margin: 0; padding: 0 }
.output_wrapper p { margin: 1.5em 0; padding-left: 1em; padding-right: 1em }
.output_wrapper h1, .output_wrapper h2, .output_wrapper h3, .output_wrapper h4, .output_wrapper h5, .output_wrapper h6 { margin: 1.5em 0; font-weight: bold; color: rgba(21, 153, 87, 1); text-align: center }
.output_wrapper h1 { font-size: 1.6em }
.output_wrapper h2 { font-size: 1.4em }
.output_wrapper h3 { font-size: 1.3em }
.output_wrapper h4 { font-size: 1.2em }
.output_wrapper h5 { font-size: 1em }
.output_wrapper h6 { font-size: 1em }
.output_wrapper ul, .output_wrapper ol { padding-left: 32px }
.output_wrapper ul { list-style-type: disc }
.output_wrapper ol { list-style-type: decimal }
.output_wrapper li * { }
.output_wrapper li { margin-bottom: 0.5em }
.output_wrapper .code_size_default { line-height: 18px; font-size: 14px; font-weight: normal; word-spacing: 0; letter-spacing: 0 }
.output_wrapper .code_size_tight { line-height: 15px; font-size: 14px; font-weight: normal; word-spacing: -3px; letter-spacing: 0 }
.output_wrapper pre code { font-family: Consolas, Inconsolata, Courier, monospace; border-radius: 0 }
.output_wrapper blockquote { display: block; padding: 15px 15px 15px 1rem; font-size: 0.9em; margin: 1em 0; color: rgba(129, 145, 152, 1); border-left: 6px solid rgba(220, 230, 240, 1); background: rgba(242, 247, 251, 1); overflow: auto; word-wrap: normal; word-break: normal }
.output_wrapper blockquote p { margin: 0 }
.output_wrapper a { text-decoration: none; color: rgba(30, 107, 184, 1); word-wrap: break-word }
.output_wrapper strong { font-weight: bold }
.output_wrapper em { font-style: italic }
.output_wrapper del { font-style: italic }
.output_wrapper strong em { font-weight: bold }
.output_wrapper hr { height: 1px; margin: 1.5rem 0; border-right: none; border-bottom: none; border-left: none; border-top: 1px dashed rgba(165, 165, 165, 1) }
.output_wrapper code { word-break: break-all; word-wrap: break-word; padding: 2px 4px; border-radius: 4px; margin: 0 2px; background: rgba(248, 248, 248, 1); font-size: 14px; font-weight: normal }
.output_wrapper img { display: block; margin: 0 auto; max-width: 100% }
.output_wrapper figcaption { margin-top: 10px; text-align: center; color: rgba(153, 153, 153, 1); font-size: 0.7em }
.output_wrapper table { display: table; width: 100%; text-align: left }
.output_wrapper tbody { border: 0 }
.output_wrapper table tr { border-top: 1px solid rgba(204, 204, 204, 1); border-right: 0; border-bottom: 0; border-left: 0; background-color: rgba(255, 255, 255, 1) }
.output_wrapper table tr th, .output_wrapper table tr td { font-size: 1em; border: 1px solid rgba(204, 204, 204, 1); padding: 0.5em 1em; text-align: left }
.output_wrapper table tr th { font-weight: bold; background-color: rgba(240, 240, 240, 1) }
.output_wrapper .katex-display { font-size: 1.22em }
.output_wrapper .katex { padding: 8px 3px }
.output_wrapper .katex-display>.katex { display: inline-block; text-align: center; padding: 3px }
.output_wrapper .katex img { display: inline-block; vertical-align: middle }
.output_wrapper a[href^=”#”] sup { vertical-align: super; margin: 0 2px; padding: 1px 3px; color: rgba(255, 255, 255, 1); background: rgba(102, 102, 102, 1); font-size: 0.7em }
.output_wrapper .task-list-list { list-style-type: none }
.output_wrapper .task-list-list.checked { color: rgba(62, 62, 62, 1) }
.output_wrapper .task-list-list.uncheck { color: rgba(191, 193, 191, 1) }
.output_wrapper .task-list-list .icon_uncheck, .output_wrapper .task-list-list .icon_check { display: inline-block; vertical-align: middle; margin-right: 10px }
.output_wrapper .task-list-list .icon_check::before { content: “√”; border: 2px solid rgba(62, 62, 62, 1); color: rgba(255, 0, 0, 1) }
.output_wrapper .task-list-list .icon_uncheck::before { content: “x”; border: 2px solid rgba(191, 193, 191, 1); color: rgba(191, 193, 191, 1) }
.output_wrapper .task-list-list .icon_check::before, .output_wrapper .task-list-list .icon_uncheck::before { padding: 2px 8px 2px 5px; border-radius: 5px }
.output_wrapper .toc { margin-left: 25px }
.output_wrapper .toc_item { display: block }
.output_wrapper .toc_left { margin-left: 25px }
body { width: 100%; margin: 0; padding: 0; background: rgba(81, 154, 178, 1) }
#export_content { margin: 40px 20%; padding: 20px; border: 1px solid rgba(149, 155, 111, 1); background: rgba(255, 255, 255, 1) }
什么是 BigDecimal为什么用 BigDecimal 而不用 double加减乘除常用方法保留两位小数四舍五入比较注意事项参考
什么是 BigDecimal
BigDecimal 可以表示一个任意大小且精度完全准确的浮点数。
为什么用 BigDecimal 而不用 double
Talk is cheap, Show me the Code.
例 1：
1double d1 = 0.3;
2double d2 = 0.2;
3System.out.println("Double:\t 0,3 - 0,2 = " + (d1 - d2));
4
5float f1 = 0.3f;
6float f2 = 0.2f;
7System.out.println("Float:\t 0,3 - 0,2 = " + (f1 - f2));
8
9BigDecimal bd1 = new BigDecimal("0.3");
10BigDecimal bd2 = new BigDecimal("0.2");
11System.out.println("BigDec:\t 0,3 - 0,2 = " + (bd1.subtract(bd2)));
运行结果
1Double: 0,3 - 0,2 = 0.09999999999999998
2Float: 0,3 - 0,2 = 0.10000001
3BigDec: 0,3 - 0,2 = 0.1
从运行结果可以得出，当我们要做精确的小数操作运算时，就需要用到 BigDecimal。那下面做一下除法运算，看看结果：
例 2：
1double d1 = 10;
2double d2 = 3;
3System.out.println("Double:\t 10 / 3 = " + (d1 / d2));
4
5float f1 = 10f;
6float f2 = 3f;
7System.out.println("Float:\t 10 / 3 = " + (f1 / f2));
8
9// Exception!
10BigDecimal bd3 = new BigDecimal("10");
11BigDecimal bd4 = new BigDecimal("3");
12System.out.println("BigDec:\t 10 / 3 = " + (bd3.divide(bd4)));
运行结果
1Double: 10 / 3 = 3.3333333333333335
2Float: 10 / 3 = 3.3333333
3Exception in thread "main" java.lang.ArithmeticException: Non-terminating decimal expansion; no exact representable decimal result.
当结果除不进，并且没有设置进位的状态值，那就会抛出异常。正确的操作如下：
1System.out.println("BigDec:\t 10 / 3 = " + (bd3.divide(bd4,4,BigDecimal.ROUND_HALF_UP)));
运行结果
1Double: 10 / 3 = 3.3333333333333335
2Float: 10 / 3 = 3.3333333
3BigDec: 10 / 3 = 3.3333
总结：当我们在精度要求非常高的时候，需要进行精确的计算，比如：货币，那我们就需要采用 java.math.BigDecimal 类来进行精确计算。
加减乘除
| 方法 | 叙述 |
|---|---|
| add(BigDecimal) | BigDecimal对象中的值相加，然后返回这个对象 |
| subtract(BigDecimal) | BigDecimal对象中的值相减，然后返回这个对象 |
| multiply(BigDecimal) | BigDecimal对象中的值相乘，然后返回这个对象 |
| divide(BigDecimal) | BigDecimal对象中的值相除，然后返回这个对象 |
1public class BigDecimalCalculation {
2 static BigDecimal a = new BigDecimal("0.02");
3 static BigDecimal b = new BigDecimal("0.03");
4
5 public static void main(String[] args) {
6 System.out.println("a + b = " + a.add(b));
7 System.out.println("a - b = " + a.subtract(b));
8 System.out.println("a * b = " + a.multiply(b));
9 System.out.println("a ÷ b = " + a.divide(b,2,BigDecimal.ROUND_HALF_UP));
10 }
11
12}
运行结果：
1a + b = 0.05
2a - b = -0.01
3a * b = 0.0006
4a ÷ b = 0.67
常用方法
保留两位小数
1public class keepTwoDecimal {
2 public static void main(String[] args) {
3 BigDecimal num= new BigDecimal(13.154215);
4
5 //方式一
6 DecimalFormat df1 = new DecimalFormat("0.00");
7 String str = df1.format(num);
8 System.out.println(str); //13.15
9
10 //方式二
11 // #.00 表示两位小数 #.0000四位小数
12 DecimalFormat df2 =new DecimalFormat("#.00");
13 String str2 =df2.format(num);
14 System.out.println(str2); //13.15
15
16 //方式三
17 //%.2f %. 表示 小数点前任意位数 2 表示两位小数 格式后的结果为f 表示浮点型
18 String result = String.format("%.2f", num);
19 System.out.println(result); //13.15
20 }
21}
四舍五入
- ROUND_UP
舍入远离零的舍入模式。
在丢弃非零部分之前始终增加数字（始终对非零舍弃部分前面的数字加 1）
例如：2.36 -> 2.4
- ROUND_DOWN
接近零的舍入模式。
在丢弃某部分之前始终不增加数字(从不对舍弃部分前面的数字加1，即截短)。
例如：2.36 -> 2.3
- ROUND_CEILING
接近正无穷大的舍入模式。
如果 BigDecimal 为正，则舍入行为与 ROUND_UP 相同;
如果为负，则舍入行为与 ROUND_DOWN 相同。
相当于是 ROUND_UP 和 ROUND_DOWN 的合集
- ROUND_FLOOR
接近负无穷大的舍入模式。
如果 BigDecimal 为正，则舍入行为与 ROUND_DOWN 相同;
如果为负，则舍入行为与 ROUND_UP 相同。
与 ROUND_CEILING 正好相反
- ROUND_HALF_UP
四舍五入
例如：2.35 -> 2.4
- ROUND_HALF_DOWN
五舍六入
例如：2.35 -> 2.3
- ROUND_HALF_EVEN
如果舍弃部分左边的数字为奇数，则舍入行为与 ROUND_HALF_UP 相同（四舍五入）;
如果为偶数，则舍入行为与 ROUND_HALF_DOWN 相同（五舍六入）。
例如：1.15 -> 1.1，1.25 -> 1.2
- ROUND_UNNECESSARY
断言请求的操作具有精确的结果，因此不需要舍入。
如果对获得精确结果的操作指定此舍入模式，则抛出 ArithmeticException。
我觉得剩下得了解下就行，而且我感觉剩下有的就是错的，比如 ROUND_HALF_DOWN 和 ROUND_HALF_EVEN，看下面的结果你就知道我说的是为什么了。
1public class BigDecimalScaleTest {
2 public static void main(String[] args) {
3 double num = 2.35;
4 BigDecimal b = new BigDecimal(num);
5 // setScale(1) 表示保留一位小数
6 System.out.println("ROUND_UP，结果：" + b.setScale(1, BigDecimal.ROUND_UP).doubleValue());
7 System.out.println("ROUND_DOWN，结果：" + b.setScale(1, BigDecimal.ROUND_DOWN).doubleValue());
8 System.out.println("ROUND_CEILING，结果：" + b.setScale(1, BigDecimal.ROUND_CEILING).doubleValue());
9 System.out.println("ROUND_FLOOR，结果：" + b.setScale(1, BigDecimal.ROUND_FLOOR).doubleValue());
10 System.out.println("ROUND_HALF_UP，结果：" + b.setScale(1, BigDecimal.ROUND_HALF_UP).doubleValue());
11 System.out.println("ROUND_HALF_DOWN，结果：" + b.setScale(1, BigDecimal.ROUND_HALF_DOWN).doubleValue());
12 System.out.println("ROUND_HALF_EVEN，结果：" + b.setScale(1, BigDecimal.ROUND_HALF_EVEN).doubleValue());
13 System.out.println("ROUND_UNNECESSARY，结果：" + b.setScale(1, BigDecimal.ROUND_UNNECESSARY).doubleValue());
14 }
15}
运行结果
1ROUND_UP，结果：2.4
2ROUND_DOWN，结果：2.3
3ROUND_CEILING，结果：2.4
4ROUND_FLOOR，结果：2.3
5ROUND_HALF_UP，结果：2.4
6ROUND_HALF_DOWN，结果：2.4 (来给我解释解释这个，说好的五舍六入呢)
7ROUND_HALF_EVEN，结果：2.4 (还有这个)
8Disconnected from the target VM, address: \'127.0.0.1:59637\', transport: \'socket\'
9Exception in thread "main" java.lang.ArithmeticException: Rounding necessary
小结：常用的就是 ROUND_HALF_UP、ROUND_UP 和 ROUND_DOWN，其它的当个笑话就行
比较
a.compareTo(b)
a > b 返回 1；a = b 返回 0；a < b 返回 -1
1public class BigDecimalCompare {
2 public static void main(String[] args) {
3 BigDecimal a = new BigDecimal("0.02");
4 BigDecimal b = new BigDecimal("0.01");
5 BigDecimal a2 = new BigDecimal("0.02");
6
7 System.out.println(" a > b 返回结果：" + a.compareTo(b));
8 System.out.println(" a = a2 返回结果：" + a.compareTo(a2));
9 System.out.println(" b < a 返回结果：" + b.compareTo(a));
10 }
11}
运行结果
1 a > b 返回结果：1
2 a = a2 返回结果：0
3 b < a 返回结果：-1
注意事项
在上面的使用中，我们都用的 String 给 BigDecimal 进行 赋值，而没有使用 double 类型赋值，具体的原因看下面的例子：
1public class BigDecimalTest {
2 public static void main(String[] args) {
3 BigDecimal num1 = new BigDecimal(0.005);
4 BigDecimal num2 = new BigDecimal(1000000);
5 BigDecimal num3 = new BigDecimal(-1000000);
6 //尽量用字符串的形式初始化
7 BigDecimal num12 = new BigDecimal("0.005");
8 BigDecimal num22 = new BigDecimal("1000000");
9 BigDecimal num32 = new BigDecimal("-1000000");
10
11 //加法
12 BigDecimal result1 = num1.add(num2);
13 BigDecimal result12 = num12.add(num22);
14 //减法
15 BigDecimal result2 = num1.subtract(num2);
16 BigDecimal result22 = num12.subtract(num22);
17 //乘法
18 BigDecimal result3 = num1.multiply(num2);
19 BigDecimal result32 = num12.multiply(num22);
20 //绝对值
21 BigDecimal result4 = num3.abs();
22 BigDecimal result42 = num32.abs();
23 //除法
24 BigDecimal result5 = num2.divide(num1,20,BigDecimal.ROUND_HALF_UP);
25 BigDecimal result52 = num22.divide(num12,20,BigDecimal.ROUND_HALF_UP);
26
27 System.out.println("加法用value结果："+result1);
28 System.out.println("加法用string结果："+result12);
29
30 System.out.println("减法value结果："+result2);
31 System.out.println("减法用string结果："+result22);
32
33 System.out.println("乘法用value结果："+result3);
34 System.out.println("乘法用string结果："+result32);
35
36 System.out.println("绝对值用value结果："+result4);
37 System.out.println("绝对值用string结果："+result42);
38
39 System.out.println("除法用value结果："+result5);
40 System.out.println("除法用string结果："+result52);
41 }
42 }
运行结果：
1加法用value结果：1000000.005000000000000000104083408558608425664715468883514404296875
2加法用string结果：1000000.005
3减法value结果：-999999.994999999999999999895916591441391574335284531116485595703125
4减法用string结果：-999999.995
5乘法用value结果：5000.000000000000104083408558608425664715468883514404296875000000
6乘法用string结果：5000.000
7绝对值用value结果：1000000
8绝对值用string结果：1000000
9除法用value结果：199999999.99999999583666365766
10除法用string结果：200000000.00000000000000000000
- System.out.println() 中的数字默认是 double 类型的，double 类型的小数计算不准确
- 使用 BigDecimal 的构造方法传入 double 类型时，计算的结果也是不准确的！
所以我们在使用 BigDecimal 进行赋值的时候，最好使用传入 String 的构造函数，可以确认精度。
参考
https://blog.csdn.net/haiyinshushe/article/details/82721234
https://www.jianshu.com/p/2947868d76eb
https://blog.csdn.net/ochangwen/article/details/51531866