Java中测试StringBuilder、StringBuffer、String在字符串拼接上的性能

应一个大量字符串拼接的任务

测试一下StringBuilder、StringBuffer、String在操作字符串拼接时候的性能

性能上理论是StringBuilder > StringBuffer > String

测试方法：

创建一个StirngTest类含有静态常量字符串是26个字母，以及一个循环轮数

在测试时采用循环来操作字符串的拼接，计算操作时间并输出：

package com.test.xlc;

import java.util.Random;

public class StringTest {

    static final String strFinal = "abcdefghijklmnopqrstovwxyz";

    static final int forInt = 100;

    static void StringBuilderTest() {

        Random rand = new Random(47);

        StringBuilder strB = new StringBuilder();

        long start = System.currentTimeMillis();

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

            int randInt = rand.nextInt(23);

            strB.append(strFinal.substring(randInt, randInt + 4));

        }

        long end = System.currentTimeMillis();

//        System.out.println(strB.toString());

        System.out.println("StringBuilderTest:" + (end - start));

    }

    static void StringBufferTest() {

        Random rand = new Random(47);

        StringBuffer strB = new StringBuffer();

        long start = System.currentTimeMillis();

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

            int randInt = rand.nextInt(23);

            strB.append(strFinal.substring(randInt, randInt + 4));

        }

        long end = System.currentTimeMillis();

//        System.out.println(strB.toString());

        System.out.println("StringBufferTest:" + (end - start));

    }

    static void StringOnly() {

        Random rand = new Random(47);

        String str = "";

        long start = System.currentTimeMillis();

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

            int randInt = rand.nextInt(23);

            str += strFinal.substring(randInt, randInt + 4);

        }

        long end = System.currentTimeMillis();

//        System.out.println(str);

        System.out.println("String:" + (end - start));

    }

    public static void main(String...args) {

        StringBuilderTest();

        StringBufferTest();

        StringOnly();

    }

}

测试循环次数：

100

StringBuilderTest:0

StringBufferTest:0

String:0

1000

StringBuilderTest:1

StringBufferTest:0

String:7

10000

StringBuilderTest:2

StringBufferTest:2

String:217

100000

StringBuilderTest:12

StringBufferTest:10

String:17136

1000000

StringBuilderTest:55

StringBufferTest:53

我提前终止了

之后我又测试了拼接长串，本实验结果显示在拼接字符串的效率上：

StringBuffer > StringBuilder > String

巴特西

Java中测试StringBuilder、StringBuffer、String在字符串拼接上的性能

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