寫程式使用 split 切割不會注意到的陷阱

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public class MyClass {
    public static void main(String args[]) {
        String str = new String("1^^2^^^3^4^5^^^^");
 
        System.out.println("^ 分隔符返回值 :" );
        int index = 0;
        for (String retval: str.split("\\^")){
            System.out.println((index++) + ":" + retval);
        }
 
    }
}

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^ 分隔符返回值 :
0:1
1:
2:2
3:
4:
5:3
6:4
7:5

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"1^2^3^4^5^^^^".split('^')
// Array(9) [ "1", "2", "3", "4", "5", "", "", "", "" ]

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"1^2^3^4^5^^^^".split(/\^/)
// Array(9) [ "1", "2", "3", "4", "5", "", "", "", "" ]

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var_dump(explode("^","1^2^3^4^5^^^^"));

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var_dump( preg_split("/\\^/", "1^2^3^4^5^^^^"));

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array(9) {
  [0]=>
  string(1) "1"
  [1]=>
  string(1) "2"
  [2]=>
  string(1) "3"
  [3]=>
  string(1) "4"
  [4]=>
  string(1) "5"
  [5]=>
  string(0) ""
  [6]=>
  string(0) ""
  [7]=>
  string(0) ""
  [8]=>
  string(0) ""
}

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import com.sun.deploy.util.StringUtils;
String s =",1,,2,3,4,,";
String[] split1 = s.split(",");
// 
String[] split2 = StringUtils.splitString(s, ",");
// 1,2,3,4