https://www.typea.info/tips_/index.php?action=history&feed=atom&title=Java_BigDecimal%E3%81%AE%E7%BD%A0 2026-04-04T08:03:30Z このウィキのこのページに関する変更履歴 MediaWiki 1.34.0 https://www.typea.info/tips_/index.php?title=Java_BigDecimal%E3%81%AE%E7%BD%A0&diff=6190&oldid=prev 2020-02-16T04:27:26Z

<p></p> <table class="diff diff-contentalign-left" data-mw="interface"> <col class="diff-marker" /> <col class="diff-content" /> <col class="diff-marker" /> <col class="diff-content" /> <tr class="diff-title" lang="ja"> <td colspan="2" style="background-color: #fff; color: #222; text-align: center;">← 古い版</td> <td colspan="2" style="background-color: #fff; color: #222; text-align: center;">2020年2月16日 (日) 04:27時点における版</td> </tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l1" >1行目:</td> <td colspan="2" class="diff-lineno">1行目:</td></tr> <tr><td class='diff-marker'>−</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>==Java BigDecimalの罠==</div></td><td class='diff-marker'>+</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>==<ins class="diffchange diffchange-inline">[[</ins>Java BigDecimalの罠<ins class="diffchange diffchange-inline">]]</ins>==</div></td></tr> <tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Java]] |  </div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Java]] |  </div></td></tr> <tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr> </table>

Piroto https://www.typea.info/tips_/index.php?title=Java_BigDecimal%E3%81%AE%E7%BD%A0&diff=5039&oldid=prev 2020-02-15T08:36:36Z

<p></p> <table class="diff diff-contentalign-left" data-mw="interface"> <col class="diff-marker" /> <col class="diff-content" /> <col class="diff-marker" /> <col class="diff-content" /> <tr class="diff-title" lang="ja"> <td colspan="2" style="background-color: #fff; color: #222; text-align: center;">← 古い版</td> <td colspan="2" style="background-color: #fff; color: #222; text-align: center;">2020年2月15日 (土) 08:36時点における版</td> </tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l1" >1行目:</td> <td colspan="2" class="diff-lineno">1行目:</td></tr> <tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Java BigDecimalの罠==</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Java BigDecimalの罠==</div></td></tr> <tr><td class='diff-marker'>−</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[Java]]</div></td><td class='diff-marker'>+</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[Java]] <ins class="diffchange diffchange-inline">| </ins></div></td></tr> <tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr> <tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>====問題の発生====</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>====問題の発生====</div></td></tr> </table>

Piroto https://www.typea.info/tips_/index.php?title=Java_BigDecimal%E3%81%AE%E7%BD%A0&diff=3341&oldid=prev 2020-02-15T08:03:28Z

<p></p> <table class="diff diff-contentalign-left" data-mw="interface"> <col class="diff-marker" /> <col class="diff-content" /> <col class="diff-marker" /> <col class="diff-content" /> <tr class="diff-title" lang="ja"> <td colspan="2" style="background-color: #fff; color: #222; text-align: center;">← 古い版</td> <td colspan="2" style="background-color: #fff; color: #222; text-align: center;">2020年2月15日 (土) 08:03時点における版</td> </tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l1" >1行目:</td> <td colspan="2" class="diff-lineno">1行目:</td></tr> <tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Java BigDecimalの罠==</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Java BigDecimalの罠==</div></td></tr> <tr><td class='diff-marker'>−</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[Java]</div></td><td class='diff-marker'>+</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins class="diffchange diffchange-inline">[</ins>[Java<ins class="diffchange diffchange-inline">]</ins>]</div></td></tr> <tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr> <tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>====問題の発生====</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>====問題の発生====</div></td></tr> </table>

Piroto https://www.typea.info/tips_/index.php?title=Java_BigDecimal%E3%81%AE%E7%BD%A0&diff=2098&oldid=prev 2020-02-15T07:33:12Z

<p>ページの作成:「==Java BigDecimalの罠== [Java] ====問題の発生==== BigDecimalを使えば、正確な演算ができると考えてしまうかもしれないが、以下の…」</p> <p><b>新規ページ</b></p><div>==Java BigDecimalの罠==<br /> [Java]<br /> <br /> ====問題の発生====<br /> BigDecimalを使えば、正確な演算ができると考えてしまうかもしれないが、以下のように、doubleからBigDecimalを生成すると、正確な値にならない。<br /> <br /> 例<br /> double d = 0.1d;<br /> java.math.BigDecimal bd = new java.math.BigDecimal(d);<br /> System.out.println(bd);<br /> <br /> 結果<br /> 0.1000000000000000055511151231257827021181583404541015625<br /> <br /> *上記例は、2進数で &quot;0.1&quot;を完全に表現できないため、発生する。<br /> *小数点以下を 1/n (n=2の乗数)の合計にて表現するため<br /> <br /> ====対処====<br /> BigDecimalを文字列から生成するとか。<br /> 例<br /> double d = 0.1d;<br /> java.math.BigDecimal bd = new java.math.BigDecimal(String.valueOf(d));<br /> System.out.println(bd);<br /> 結果<br /> 0.1</div>

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