Java - StringIndexOutOfBoundsException

Question

First of all, here is the problematic part of my code; these are very basic classes

public Passenger(String Name, String adress, String number, String password){
    count++;
    accId+=count;

    this.Name=Name;

    this.adress=adress;
    this.number=number;

    if(checkPw(password)==true){
        this.password=password;
    }

}

private boolean checkPw(String password){
    int length;
    length = password.length();

    if(length != 6){
        return false;
    }
    else if(password.charAt(0)==0){
        return false;
    }
    else {
        for (int i = 0; i < password.length();i++){
            if((password.charAt(i))==(password.charAt(i+1))){
                return false;
            }
        }
    }
    return true;        
}

testClass:

public static void main(String[] args){
    Passenger gokhan=new Passenger("Gokhan","Istanbul","xxx","254651");

    System.out.println(gokhan.password);
}

So, I think the problem is in the Passenger class. Its my first time that class in class things (I meant the if(checkPw(password)==true) part). In the test class, it looks very clear and I never thought that this error will appear. How can I avoid this message?

Full error:

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 6
    at java.lang.String.charAt(String.java:658)
    at project1.Passenger.checkPw(Passenger.java:45)
    at project1.Passenger.<init>(Passenger.java:27)
    at project1.testClass.main(testClass.java:11)

Java Result: 1

score 5 · Accepted Answer · answered Oct 29 '13 at 22:28

The problem is here :

for (int i = 0; i < password.length();i++){
    if((password.charAt(i))==(password.charAt(i+1))){
        return false;
    }
 }

When you're in the last iteration, you're trying to access the char in the string at the position i+1 which doesn't exists.

    text
       ^
       |
when i = 3 charAt(i) will return t and charAt(i+1) will throw the exception

score 2 · Answer 2 · answered Oct 29 '13 at 22:30

This line appears to be the problem:

if((password.charAt(i))==(password.charAt(i+1))){

When on the last iteration of the for loop, i is 5 and i+1, or 6, goes off the end of the string, because indexes range from 0 to length() - 1. The solution here is to stop the for loop iteration after the second-to-last character instead of the last character. Change

for (int i = 0; i < password.length();i++){

to

for (int i = 0; i < password.length() - 1; i++){

So that the maximum value i has in the for loop is 4, so i+1 or 5 isn't off the end of the string.

Java - StringIndexOutOfBoundsException

2 Answers2

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