小编Joh*_*ohn的帖子

我做了一个性能测试

    String test="";
    Date st = new Date();
    logger.info("start "+(new Date()).toString());
    for(int i = 0;i<100000;i++) {
        test += "test";  
    }
    logger.info("end "+(new Date()).toString());

    test="";
    StringBuilder sb = new StringBuilder(test);
    logger.info("start Sb "+(new Date()).toString());
    for(int i = 0;i<100000;i++) {
        sb.append("test");  
    }
    test = sb.toString();
    logger.info("end sb "+(new Date()).toString());

结果是

start Fri Jun 30 10:34:42 KRAT 2017
end Fri Jun 30 10:34:55 KRAT 2017
start Sb Fri Jun 30 10:34:55 KRAT 2017
end sb Fri Jun 30 10:34:55 KRAT 2017

相差13秒！！！

但我到处都看到“+”运算符更快的标语，因为从 …