StringBulider、StringBuffer、String效率比较

亦凉 2021-09-22 00:24 366阅读 0赞

效率的比较：  
\`public class StringTest \{

public static void main(String[] args) {
        test();
    }
    
    public static void test(){
        /**
         * @author:huazeqi
         * @Date:2021/6/4 23:15
         * @Description:String效率测试
         **/
        String str = "hua";
        long l = System.currentTimeMillis();
        for (int i = 0; i < 100000; i++) {
            str = str + "zeqi";
        }
        long l1 = System.currentTimeMillis();
        System.out.println("String耗时：" + (l1 - l));
        /**
         * @author:huazeqi
         * @Date:2021/6/4 23:15
         * @Description:StringBuffer效率测试
         **/
        StringBuffer stringBuffer = new StringBuffer();
        stringBuffer.append("hua");
        long l2 = System.currentTimeMillis();
        for (int i = 0; i < 100000000; i++) {
            stringBuffer = stringBuffer.append("zeqi");
        }
        long l3 = System.currentTimeMillis();
        System.out.println("StringBuffer耗时：" + (l3 - l2));
        /**
         * @author:huazeqi
         * @Date:2021/6/4 23:15
         * @Description:StringBuilder效率测试
         **/
        StringBuilder stringBuilder = new StringBuilder();
        stringBuilder.append("hua");
        long l4 = System.currentTimeMillis();
        for (int i = 0; i < 100000000; i++) {
            stringBuilder = stringBuilder.append("zeqi");
        }
        long l5 = System.currentTimeMillis();
        System.out.println("StringBuilder耗时：" + (l5 - l4));
    }

\}  
\`![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzQ5NTM5MA_size_16_color_FFFFFF_t_70]  
由此可以得出拼接效率：StringBuilder>StringBuffer>String。  
同时测试出百万级以内，StringBuilder和StringBuffer差别不大，百万级以上区别明显，当然这跟计算机计算能力有关  
至于为什么StringBuilder效率大于StringBuffer见下图：![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzQ5NTM5MA_size_16_color_FFFFFF_t_70 1][]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzQ5NTM5MA_size_16_color_FFFFFF_t_70 2]  
StringBuffer对方法做了线程安全处理，而StringBuilder并没有做线程安全处理，提高了线程安全，牺牲了效率。  
。

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