文字替换之效率

1. 常用方法

 a) public String replace(char oldChar, char newChar) （文本）

 b) public String replace(CharSequence target, CharSequence replacement)（文本）

 c) public String replaceAll(String regex, String replacement) （表达式）

 d) commons-lang-2.1:org.apache.commons.lang.StringUtils（文本）

 e) Matcher.replaceAll(String replacement)（表达式）

 

2. 小误差验证

 

int count = 10*10000;
String str = "127.0.0.1";
{
	System.out.print(str.replace('.', '_'));
	long b = System.nanoTime();
	for (int i = 0; i < count; i++) {
		str.replace('.', '_');
	}
	System.out.println("  basic-char  :"+(System.nanoTime()-b));

}
{
	System.out.print(str.replace(".", "_"));
	long b = System.nanoTime();
	for (int i = 0; i < count; i++) {
		str.replace("\\.", "_");
	}
	System.out.println("  CharSequence:"+(System.nanoTime()-b));
}

{
	System.out.print(str.replaceAll("\\.", "_"));
	long b = System.nanoTime();
	for (int i = 0; i < count; i++) {
		str.replaceAll("\\.", "_");
	}
	System.out.println("  replaceAll  :"+(System.nanoTime()-b));
}

{
	//commons-lang-2.1:org.apache.commons.lang.StringUtils
	System.out.print(StringUtils.replace(str, ".", "_"));
	long b = System.nanoTime();
	for (int i = 0; i < count; i++) {
		StringUtils.replace(str, ".", "_");
	}
	System.out.println("  StringUtils :"+(System.nanoTime()-b));
}

{
	Matcher m = Pattern.compile(".", Pattern.LITERAL).matcher(str);
	System.out.print(m.replaceAll("_"));
	long b = System.nanoTime();
	for (int i = 0; i < count; i++) {
		m.reset();
		m.replaceAll("_");
	}
	System.out.println(" *CharSequence:"+(System.nanoTime()-b));
}

{
	Matcher m = Pattern.compile("\\.").matcher(str);
	System.out.print(m.replaceAll("_"));
	long b = System.nanoTime();
	for (int i = 0; i < count; i++) {
		m.reset();
		m.replaceAll("_");
	}
	System.out.println(" *REGEXP      :"+(System.nanoTime()-b));
}

 

3. 鲁莽结论
输出

127_0_0_1 basic-char :9919554
127_0_0_1 CharSequence:73282416
127_0_0_1 replaceAll :209326220
127_0_0_1 StringUtils :69380801
127_0_0_1 *CharSequence:160218838
127_0_0_1 *REGEXP :158787441

 

结论

 

basic-char >> （StringUtils ≈ CharSequence）>> REGEXP >replaceAll

 

4. 注意事项

 

参数为正则表达式的时候，需要字符转义，如 ^.$?*+等