Test_StringBuilder

package com.company.danei;

/**
 * @Author:
 * @Date: 2021-05-09
 * @Description: 验证StringBuilder的执行效率,通过StringBuilder的append（）方法拼接字符串，效率比+拼接高出1000倍
 **/


public class Test_StringBuilder {
    public static void main(String[] args) {
        String str = "abcdefghicklmnopqestuvwxyz";
        method(str);
        method2(str);
    }

    /**
     * 通过StringBuilder拼接字符串，计算执行效率
     * @param str
     */
    private static void method2(String str) {
        StringBuilder sb = new StringBuilder();
        Long s1 = System.currentTimeMillis();
        for (int i = 0; i < 10000; i++) {
           sb.append(str);
        }
        Long s2= System.currentTimeMillis();
        System.out.println(s2-s1);//1ms
    }

    /**
     * 通过+连接字符串
     * 计算程序执行效率
     * @param str
     */
    private static void method(String str) {
        String str1="";
        Long s1 = System.currentTimeMillis();
        for (int i = 0; i < 10000; i++) {
            str1 += str;
        }
        Long s2= System.currentTimeMillis();
        System.out.println(s2-s1);//1445ms
    }
}