字符串后n位用*号代替各方法效率评测，字符串,/** * */pac

字符串后n位用*号代替各方法效率评测，字符串,/** * */pac

/** *  */package com.comm;public class Comm{    /**     * 第一种方法，把字符串的后n位用“*”号代替     *      * @param str     *            要代替的字符串     * @param n     *            代替的位数     * @return     */    public static String replaceSubString(String str, int n)    {        String sub = "";        sub = str.substring(0, str.length() - n);        StringBuffer sb = new StringBuffer();        for (int i = 0; i < n; i++)        {            sb = sb.append("*");        }        sub += sb.toString();        return sub;    }    /**     * 第二种方法     *      * @param org     * @param n     * @return     */    public static String replaceString(String org, int n)    {        char[] cs = org.toCharArray();        int len = org.length();        for (int i = 0; i < n; i++)        {            cs[len - i - 1] = '*';        }        return String.valueOf(cs);    }    /**     * 第三种方法     *      * @param org     * @param n     * @return     */    public static String replaceString3(String org, int n)    {        StringBuffer sb = new StringBuffer(org.substring(0, org.length() - n));        for (int i = 0; i < n; i++)        {            sb.append('*');        }        return sb.toString();    }    /**     * @param args     */    public static void main(String[] args)    {        String str = "13560732344ssssssssssssssssssfffffffffff";        int n = 10;        int times = 1000000;        System.out.println("第一种结果：" + replaceSubString(str, n));        System.out.println("第二种结果：" + replaceString(str, n));        System.out.println("第三种结果：" + replaceString3(str, n));        long tm1 = System.currentTimeMillis();        for (int i = 0; i < times; i++)        {            replaceSubString(str, n);        }        long tm2 = System.currentTimeMillis();        for (int i = 0; i < times; i++)        {            replaceString(str, n);        }        long tm3 = System.currentTimeMillis();        for (int i = 0; i < times; i++)        {            replaceString3(str, n);        }        long tm4 = System.currentTimeMillis();        System.out.println("第一种方法用时：" + (tm2 - tm1));        System.out.println("第二种方法用时：" + (tm3 - tm2));        System.out.println("第三种方法用时：" + (tm4 - tm3));    }}//该片段来自于http://byrx.net