Java统计一个字符串在另外一个字符串出现次数的方法

package me.chunsheng.javatest;import java.util.regex.Matcher;import java.util.regex.Pattern;/** * Created by wei_spring on 16/10/11. * <p> * 统计一个字符串在另外一个字符串出现的次数 * 正则匹配的方法,前提字符串不是特殊字符串 * eg:finder("adadadadauuada", "ada") 这样会统计不准确的. * 另外一个遍历的解决了上面那种情况. * 两者时间如下(纳秒为单位): 正则明显耗时,正则本就不是统计用的!!! * finder:3 * finderTime:1579549 * getCount:4 * getCountTime:34506 */public class SubStringCount {  public static void main(String[] args) {    System.out.println("武林网测试结果：");    long current1 = System.nanoTime();    System.out.println("finder:" + finder("adadadadauuada", "ada"));    System.out.println("finderTime:" + (System.nanoTime() - current1));    long current2 = System.nanoTime();    System.out.println("getCount:" + getCount("adadadadauuada", "ada"));    System.out.println("getCountTime:" + (System.nanoTime() - current2));  }  public static int getCount(String source, String sub) {    int count = 0;    int length = source.length() - sub.length();    for (int i = 0; i < length; i++) {      String sourceBak = source.substring(i, i + sub.length());      int index = sourceBak.indexOf(sub);      if (index != -1) {        count++;      }    }    return count;  }  public static int finder(String source, String regexStr) {    String regex = "[a-zA-Z]+";    if (regexStr != null && !regexStr.equals("")) {      regex = regexStr;    }    Pattern expression = Pattern.compile(regex);    Matcher matcher = expression.matcher(source);    int n = 0;    while (matcher.find()) {      n++;    }    return n;  }}