Java使用System.currentTimeMillis()方法计算程序运行时间的示例代码

/**
 * Java使用System.currentTimeMillis()方法计算程序运行时间
 * @author pan_junbiao
 **/
public class CurrentTimeTest
{
    /**
     * 使用String类型拼接字符串耗时
     */
    public static void testString()
    {
        String s = "Hello";
        String s1 = "World";
        long start = System.currentTimeMillis();
        for(int i=0; i<10000; i++)
        {
            s+=s1;
        }
        long end = System.currentTimeMillis();
        long runTime = (end - start);
        System.out.println("使用String类型拼接字符串耗时：" + runTime + "毫秒");
    }
 
    /**
     * 使用StringBuilder类型拼接字符串耗时
     */
    public static void testStringBuilder()
    {
        StringBuilder s = new StringBuilder("Hello");
        String s1 = "World";
        long start = System.currentTimeMillis();
        for(int i=0; i<10000; i++)
        {
            s.append(s1);
        }
        long end = System.currentTimeMillis();
        long runTime = (end - start);
        System.out.println("使用StringBuilder类型拼接字符串耗时：" + runTime + "毫秒");
    }
 
    public static void main(String[] args)
    {
        testString();
        testStringBuilder();
    }
}