CODEWITHSUNDEEP
javastring
Michael Peterson
Michael Peterson

Reputation: 49

How to fix String index out of range: -1

I have been working on a generating password method that will change every "S" to $.

Note I take the phrase in from another class and it will always be greater than 8 characters 

    String key;
    String store;
    key = phrase.substring(0,1).toUpperCase();
    phrase = key + phrase.substring(1,phrase.length());
    System.out.println(phrase);
    System.out.println(phrase.length());
    for(int i = phrase.length(); i>0; i--) {
        int sKey = phrase.indexOf('S');
        store = "$" + phrase.substring(sKey+1,phrase.length());
        phrase =phrase.substring(0,sKey)+store;
        System.out.print(phrase);
    }
}

However I always get this error afterwards

Exception in thread "main" Te$taaaajava.lang.StringIndexOutOfBoundsException: String index out of range: -1
    at java.lang.String.substring(Unknown Source)
    at edu.ilstu.Security.generatePassword(Security.java:15)
    at edu.ilstu.SecurityApp.main(SecurityApp.java:57)

Upvotes: 1

Views: 3295

Answers (3)

Davislor
Davislor

Reputation: 15144

You take phrase.indexOf('S') on a string without checking the return value. If there is no match, the method returns -1. You then use this index as the upper bound of a substring, which crashes the program.

You would want a different algorithm even if you got it correct, if I understand correctly what you want to do. There is no reason both to search the string for each occurrence of the character you want and also to write a loop decrementing the length by 1. Also, avoid copying long arrays and strings if possible.

Upvotes: 1

Michael Peterson
Michael Peterson

Reputation: 49

I am not sure if this is the correct way to do it. However, I have found adding an if statement actually fixed this code and stopped the for loop when the index becomes -1

    String key;
    String store;
    key = phrase.substring(0,1).toUpperCase();
    phrase = key + phrase.substring(1,phrase.length());
    for(int i = phrase.length(); i>0; i--) {
            int sKey = phrase.indexOf('S');
            if(sKey >= 0) {
            store = "$" + phrase.substring(sKey+1,phrase.length());
            phrase =phrase.substring(0,sKey)+store;
            }else {
                i=0;
            }
    }```

Upvotes: 0

GokuMizuno
GokuMizuno

Reputation: 543

Index out of range exception value of -1 means the requested symbol, in this case, S, is not found.

Upvotes: 2

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