java Clone和New哪个更快_闪出光芒

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java Clone和New哪个更快

(2010-02-03 18:00:50)

标签：

杂谈

分类： java

Clone和new哪个更快呢，这个问题的答案不是一定的，要根据实际情况决定：
情况一：对象简单，这个时候new更快，测试代码如下：

http://www.blogjava.net/Images/dot.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />{
http://www.blogjava.net/Images/dot.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />{
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />        Object obj = null ;
http://www.blogjava.net/Images/dot.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />{
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />            obj = super.clone();
http://www.blogjava.net/Images/dot.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />{
http://www.blogjava.net/Images/OutliningIndicators/ExpandedSubBlockEnd.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />        }
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />        return obj;
http://www.blogjava.net/Images/OutliningIndicators/ExpandedSubBlockEnd.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />    }
http://www.blogjava.net/Images/OutliningIndicators/ExpandedBlockEnd.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />}
http://www.blogjava.net/Images/dot.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />{
http://www.blogjava.net/Images/dot.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />{
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />        TestObj obj=new TestObj();
http://www.blogjava.net/Images/dot.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />{
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />            obj.clone();
http://www.blogjava.net/Images/OutliningIndicators/ExpandedSubBlockEnd.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />        }
http://www.blogjava.net/Images/OutliningIndicators/ExpandedSubBlockEnd.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />    }
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />
http://www.blogjava.net/Images/dot.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />{
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />        TestObj obj=new TestObj();
http://www.blogjava.net/Images/dot.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />{
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />            obj=new TestObj();
http://www.blogjava.net/Images/OutliningIndicators/ExpandedSubBlockEnd.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />        }
http://www.blogjava.net/Images/OutliningIndicators/ExpandedSubBlockEnd.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />    }
http://www.blogjava.net/Images/OutliningIndicators/ContractedSubBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />
http://www.blogjava.net/Images/dot.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />{
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />        long start;
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />        long stop;
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />        int times=1000000;
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />        System.gc();
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />        start=System.currentTimeMillis();
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />        newTest(times);
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />        stop=System.currentTimeMillis();
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />        System.out.println("newTest Time:"+(stop-start));
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />        System.gc();
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />        start=System.currentTimeMillis();
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />        cloneTest(times);
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />        stop=System.currentTimeMillis();
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />        System.out.println("cloneTest Time:"+(stop-start));
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />
http://www.blogjava.net/Images/OutliningIndicators/ExpandedSubBlockEnd.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />    }
http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />
http://www.blogjava.net/Images/OutliningIndicators/ExpandedBlockEnd.gifClone和New哪个更快" TITLE="java Clone和New哪个更快" />}

情况二：对象复杂，例如一个包括集合类的类的对象。而且这个对象的Clone使用的浅拷贝。（其实快主要是快在这个地方）
不用例子了，浅拷贝只是引用的复制，肯定比复制快。

还有一些其它的情况，但总体来说，随着对象的复杂，clone越来越快，new越来越慢。不过在使用clone的时候
一定要想清楚再用，浅拷贝使用不当会出现很多问题。

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