字符串操作

编程语言中大都有对字符串的操作的函数的封装，我们常用的一些操作有：判断是不是含有xxx，把xx替换为yy，将字符串中逗号为分割分成数组等等。下面我们来简单罗列下这些函数：

功能	Java	C#	Php	Python	JavaScript
索引	charAt	[]	[]	[]	[]/charAt
含有	contains	Contains			includes
首位	startsWith endsWith	StartsWith EndsWith		startswith endswith	startsWith endWith
字符(串)位置	indexOf lastIndexOf	IndexOf LastIndexOf	strops strrpos	index	indexOf lastIndexOf
截取	substring	SubString	substr	[s:e]	substr/substring
替换	replace	Replace	str_replace preg_replace	replace	replace
	replaceAll
拆分	split	Split	str_split	split	split
修剪	trim	Trim TrimEnd/TrimStart	trim		Trim trimLeft/trimRight
大小写转换	toUpperCase toLowerCase	ToUpperCase ToLowerCase	strtouppercase strtolowercase	lower upper	toUpperCase toLowerCase
补全		Pad PadLeft/PadRight	str_pad		padEnd padStart

java

    public static void main(String[] args){
        String str="123,abc";
        println(str.charAt(2));          //3
        println(str.contains("3,a"));   //true
        println(str.startsWith("123")); //true
        println(str.endsWith("abc"));   //true
        println(str.indexOf(","));      //3
        println(str.substring(2,4));    //3,
        println(str.replace(",","VV"));//123VVabc
        println(Arrays.toString(str.split(",")));//[123,abc]
        println(" 123  ".trim());       //123
        println(str.toUpperCase());      //123,ABC
        println(str.toUpperCase().toLowerCase());//123,abc
    }
    static void println(Object obj){
        System.out.println(obj);
    }

C#

static void Main(string[] args)
{
    var str = "123,abc";
    print(str[2]);                  //3
    print(str.Contains(","));       //True
    print(str.StartsWith("123"));   //True
    print(str.EndsWith("abc"));     //True
    print(str.IndexOf(","));        //3
    print(str.Substring(2, 4));     //3,ab
    print(str.Replace(",","VV"));   //123VVabc
    Array.ForEach(
        str.Split(','),x=>print(x)  //123 abc
    );  
    print("  123 ".Trim());         //123
    print(str.ToUpper());           //123,ABC
    print(str.ToUpper().ToLower()); //123,abc
    print(str.PadRight(9, 'p'));    //123,abcpp
    Console.ReadKey();
}
static void print(Object obj) {
    Console.WriteLine(obj);
}

php

$a='123,abc';
echo $a[2]."<br>";            //3
echo strpos($a,',a')."<br>";  //3
echo substr($a,2,4)."<br>";   //3,ab
echo str_replace(',','VV',$a)."<br>";//123VVabc
print_r(str_split($a,3));echo "<br>";  //123,abc
echo strtoupper($a)."<br>";   //123,ABC
echo strtolower("123.ABC")."<br>";  //123,abc

python

str="123,abc"
print(str[2])               #3
print(str.startswith('123'))#True
print(str.endswith('abc'))  #True
print(str.index(','))       #3
print(str[2:4])             #3,
print(str.replace(',','VV'))#123VVabc
print(str.split(','))       #['123','abc']
print(str.upper())          #123,ABC
print(str.upper().lower())  #123,abc

JavaScript

var str='123,abc';
console.log(str[2]);                  //3
console.log(str.includes(','));       //true
console.log(str.startsWith("123"));   //true
console.log(str.endsWith("abc"));     //true
console.log(str.indexOf(','));        //3
console.log(str.lastIndexOf(','));    //3
console.log(str.substr(2,4));         //3,ab
console.log(str.substring(2,4));      //3,
console.log(str.replace(",","VV"));   //123VVabc
console.log(str.split(','));          //["123","abc"]
console.log("  123 ".trim());         //123
console.log(str.toUpperCase());       //123,ABC
console.log(str.toUpperCase().toLowerCase());//123,abc
console.log(str.padEnd(9,"p"));       //123.abcpp