一种快速判断是否为质数的方法
<div style="padding-right: 5.4pt; padding-left: 5.4pt; background: #e6e6e6; padding-bottom: 4px; width: 95%; padding-top: 4px;">http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockStart.gifhttp://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedBlock.gif public static boolean isprime(int x) ...{http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gifhttp://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedSubBlock.gif if (x <= 7) ...{
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif if (x == 2 || x == 3 || x==5 || x == 7)
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http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockEnd.gif }
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif int c = 7;
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif if (x % 2 == 0)
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif return false;
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif if (x % 3 == 0)
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif return false;
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif if (x % 5 == 0)
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif return false;
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif int end = (int) Math.sqrt(x);
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gifhttp://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedSubBlock.gif while (c <= end) ...{
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http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif return false;
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockEnd.gif }
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif c += 4;
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gifhttp://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedSubBlock.gif if (x % c == 0) ...{
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif return false;
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockEnd.gif }
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif c += 2;
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gifhttp://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedSubBlock.gif if (x % c == 0) ...{
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif return false;
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockEnd.gif }
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif c += 4;
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gifhttp://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedSubBlock.gif if (x % c == 0) ...{
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif return false;
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockEnd.gif }
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif c += 2;
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gifhttp://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedSubBlock.gif if (x % c == 0) ...{
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif return false;
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockEnd.gif }
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif c += 4;
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gifhttp://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedSubBlock.gif if (x % c == 0) ...{
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif return false;
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockEnd.gif }
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif c += 6;
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gifhttp://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedSubBlock.gif if (x % c == 0) ...{
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif return false;
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockEnd.gif }
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif c += 2;
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gifhttp://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedSubBlock.gif if (x % c == 0) ...{
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif return false;
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockEnd.gif }
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif c += 6;
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockEnd.gif }
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif return true;
http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockEnd.gif }
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