Java获取字符串的子字符串

Question

I have 2 strings as shown below:

String paramNum = "99999256";
String opCode = "99999";

On the String paramNum I want to extract that part of the string which appears after the string value contained in opCode

So with the above example: the result should be "99999256" - "99999" = "256" . Parse paramNum ( 99999256 ) and reach to a position of after 99999 and then do a substring till end of the string. But I am not sure on how to reach to that position?

Note this is only a symbolic representation of what I want to do with these strings and they do mean a subtraction on 2 int.

Answer 1

One way of 100+ possible ways:

String res = paramNum.replace(opCode,"");

Visit the String API to fuel your creative fire.

If you want to replace only first match, you can:

String res = paramNum.replaceFirst(opCode,"");

Answer 2

Using String#substring :

int indexOfOpCode = paramNum.indexOf(opCode);
if(indexOfOpCode != -1) {
    String extractedStr = paramNum.substring(indexOfOpCode + opCode.length());
    ...
}

Answer 3

I came with the below:

if (paramNum.startsWith(opCode)) { // This can be - if (paramNum.contains(opCode)) {
   String res = paramNum.substring(opCode.length(), paramNum.length());
}

Note that for my case the string that I want to find always appears at the beginning...

Answer 4

One of the way:

String opcode;

String res= paranum.replaceAll(opcode," ");

Will replace all the occurrence of opcode string with space...whereas in place of opcode you can also give regular expression as a string...