Java中加号和StringBuilder进行字符串连接的效率比较

分类：Java, Java语言阅读 (2,355) Add comments

6月 202015

转载请注明原文地址：http://bcoder.com/java/speed-compare-of-plus-and-stringbuilder-when-concat-string

注意：在Java8中默认使用StringBuilder进行字符串进行拼接

下面代码对字符串进行10000次加号连接和StringBuilder连接操作：

public class StringBuilderTest {
    public static void main(String[] args){
        long time = System.currentTimeMillis();
        System.out.println("begin: " + time);

        String str = "";
        for(int i=0; i<10000; i++){
            str = str + "a1" + 1 + "a2";
        }

        long time1 = System.currentTimeMillis();

        StringBuilder sb = new StringBuilder();
        for(int i=0; i<10000; i++){
            //sb.delete(0, sb.length());
            sb.append("a1");
            sb.append(1);
            sb.append("a2");
        }

        long time2 = System.currentTimeMillis();

        System.out.println(str);
        System.out.println(sb.toString());
        System.out.println("加号耗时： " + (time1 - time));
        System.out.println("StringBuilder耗时： " + (System.currentTimeMillis() - time1));
    }
}

public class StringBuilderTest {

public static void main(String[] args){

long time = System.currentTimeMillis();

System.out.println("begin: " + time);

String str = "";

for(int i=0; i<10000; i++){

str = str + "a1" + 1 + "a2";

}

long time1 = System.currentTimeMillis();

StringBuilder sb = new StringBuilder();

for(int i=0; i<10000; i++){

//sb.delete(0, sb.length());

sb.append("a1");

sb.append(1);

sb.append("a2");

}

long time2 = System.currentTimeMillis();

System.out.println(str);

System.out.println(sb.toString());

System.out.println("加号耗时： " + (time1 - time));

System.out.println("StringBuilder耗时： " + (System.currentTimeMillis() - time1));

}

最后得到的结果如下：

加号耗时： 563
StringBuilder耗时： 7

1 2	加号耗时： 563 StringBuilder耗时： 7

由此可见效率差了80倍

注意：

StringBuffer为线程安全的字符串操作类，由于需要处理多线程同步问题，效率比StringBuilder要低

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