java和javascript中实现substr_count
php中的方法真是不少，今天觉得自己实现一下substr_count。
由于今天比较忙，就没自己想实现方法，google了一下，发现了3种，其中的两个方法真是巧妙，我要是自己实现估计只能想到第一，也就是看起来最笨的那个。不过考虑一下性能，笨方法居然是最快的
java的实现有了，javascript就很好办了
调试过程中发现了几个问题，
第一， java的当字符串很长的时候replaceAll方法会抛outofmemory异常，字串匹配的越多，需要的内存就越大。给eclipse加上如下参数可以增加虚拟机的内存-Xms32m -Xmx256m
第二， 也就是昨天发现的javascript的replace方法，只有以/tan/g形式才能替换所有的字串，但目前只找到这种hardcode的方法，不知道怎么通过变量实现
由于今天比较忙，就没自己想实现方法，google了一下，发现了3种，其中的两个方法真是巧妙，我要是自己实现估计只能想到第一，也就是看起来最笨的那个。不过考虑一下性能，笨方法居然是最快的
package util;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
/**
* This class is used to test the performance of the method for getting how
***
**/
public class CountSubString {
public static void main(String[] args) throws Exception{
CountSubString count = new CountSubString();
String source = "";
String sub = "tan";
StringBuffer sb = new StringBuffer();
for (int i = 0; i < 1000000; i++) {
sb.append("tan");
sb.append("tory");
sb.append("eddie");
}
source = sb.toString();
//String newSource = count.replace("tan", "aa", source);
String newSource = source.replaceAll("t", "aa");
//System.out.println(newSource);
//File outPut = new File("d:/eclipse3.4/outputfile.dat");
BufferedWriter bw = new BufferedWriter(new FileWriter("d:/eclipse3.4/outputfile.dat"));
bw.write(newSource);
bw.flush();
bw.close();
long timeStart = System.currentTimeMillis();
int subStringCount = count.getCountByChar(source, sub);
long timeEnd = System.currentTimeMillis();
System.out.println("Sub String occurs times is: " + subStringCount);
System.out.println("The method getCountByChar consumes " + (timeEnd - timeStart));
timeStart = System.currentTimeMillis();
subStringCount = count.getCountByReplace(source, sub);
timeEnd = System.currentTimeMillis();
System.out.println("Sub String occurs times is: " + subStringCount);
System.out.println("The method getCountByReplace consumes " + (timeEnd - timeStart));
timeStart = System.currentTimeMillis();
subStringCount = count.getCountBySplit(source, sub);
timeEnd = System.currentTimeMillis();
System.out.println("Sub String occurs times is: " + subStringCount);
System.out.println("The method getCountBySplit consume " + (timeEnd - timeStart));
}
public int getCountByChar(String source, String sub) {
int count = 0;
int pos = source.indexOf(sub.charAt(0));
do {
next: if (pos > -1) {
// boolean isEqual = true;
for (int j = 1; j < sub.length(); j++) {
if (source.charAt(pos + j) != sub.charAt(j)) {
// isEqual = false;
break next;
}
}
// if (isEqual)
count++;
}
pos = source.indexOf(sub.charAt(0), pos + 1);
} while (pos != -1);
return count;
}
public int getCountBySplit(String source, String sub) {
int count = 0;
String[] sourceArray = source.split(sub);
count = sourceArray.length - 1;
return count;
}
public int getCountByReplace(String source, String sub) {
int count = 0;
count = (source.length() - source.replaceAll(sub, "").length()) / sub.length();
return count;
}
}
java的实现有了，javascript就很好办了
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<title>Sub String Count</title>
<head>
<script type="text/javascript">
//get the count of the sub string occurs in the source
function getCountByChar(source, sub) {
var count = 0;
var pos = source.indexOf(sub.charAt(0));
do {
//next:
if (pos > -1) {
var isEqual = true;
for (var i = 1; i < sub.length; i++) {
if (source.charAt(pos + i) != sub.charAt(i)) {
isEqual = false;
break;
}
}
if (isEqual)
count++;
}
pos = source.indexOf(sub.charAt(0), pos + 1);
} while(pos > -1)
return count;
}
function getCountBySplit(source, sub) {
var count = 0;
count = source.split(sub).length - 1;
return count;
}
function getCountByReplace(source, sub) {
var count = 0;
var replacSource = source.replace(/tan/g, "");
count = (source.length - replacSource.length) / (sub.length) ;
return count;
}
function capSentence() {
var str = document.getElementById("content").value;
var result = document.getElementById("resultDiv");
result.innerHTML = str + escape("Programming PHP啊");
document.getElementById("resultChar").value = getCountByChar(str, "tan") + "getCountByChar";
document.getElementById("resultSplit").value = getCountBySplit(str, "tan") + "getCountBySplit";
document.getElementById("resultReplace").value = getCountByReplace(str, "tan") + "getCountByReplace" ;
}
</script>
<style type="text/css">
input.cap {text-transform: capitalize;}
</style>
</head>
<body>
<input id="content" class="cap" type="text" />
<input type="button" onclick="capSentence();" value="Capitaliz" />
<div id="resultDiv"></div>
<input id="resultChar" type="text" />
<input id="resultSplit" type="text" />
<input id="resultReplace" type="text" />
</body>
</html>
调试过程中发现了几个问题，
第一， java的当字符串很长的时候replaceAll方法会抛outofmemory异常，字串匹配的越多，需要的内存就越大。给eclipse加上如下参数可以增加虚拟机的内存-Xms32m -Xmx256m
第二， 也就是昨天发现的javascript的replace方法，只有以/tan/g形式才能替换所有的字串，但目前只找到这种hardcode的方法，不知道怎么通过变量实现