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RoyalUp
Asked: 2020-03-23 01:45:41 +0800 CST 2020-03-23 01:45:41 +0800 CST

Remove last element from String

  • 772

I have this code in Java:

for(int i=0;i<num;i++){
        if(i!=0){
            r = r + "+";
        }
        if(ProblemaVagones.listaVagones.get(i).isElectricidad()){
            r = r + "x" + i;
            r.substring(0, r.length()-1);       
        }
    }

My output from this piece of code is this:

x0+x1+x2+<=2;

Which is wrong because at the end it has a "+" that is left over, I have tried to make a substring from 0 to the penultimate element of the string to remove it, from what you see it does not work. Does anyone see the error?

java

2 Answers

  1. You have to retrieve the result of the substring in a String (which can be the same on which you execute the operation):

    r = r.substring(0, r.length()-1);
    • 1
  2. Best Answer

    Inside the loop it checks if it iis in a different position than the last one. Your code would look like this:

    for(int i = 0; i < num; i++){
    if(i != 0 && i != (num - 1)){
        r = r + "+";
    }
    if(ProblemaVagones.listaVagones.get(i).isElectricidad()){
        r = r + "x" + i;     
    }
}
    • 1