Something wrong with string to integer conversion

Question

I make chessboard, where alone king will walk according to the rules of chess. Below it's method to make, it called for 2 times for i and j coordinate of King, I Made input variable String to check if this King's coordinates already exist. Than I try to convert it to integer, seems something wrong with this conversion.

import java.util.*;
public class King {
    int move(String iK){
        Random rand = new Random();
        Integer coordinateKing = Integer.valueOf(iK);
        if (iK == null){           
            coordinateKing = rand.nextInt(8);
        }else{
            int caseI;
            switch(caseI = rand.nextInt(2)){
                case 0: if (coordinateKing < 8){ coordinateKing++; } else {caseI = rand.nextInt(2);}
                break;
                case 1: if (coordinateKing > 0){ coordinateKing--; } else {caseI = rand.nextInt(2);}
                break;
                default: 
                break;
            }           
        }       
        return coordinateKing;
    }
}

I have problem like this:

Exception in thread "main" java.lang.NumberFormatException: null
    at java.lang.Integer.parseInt(Integer.java:454)
    at java.lang.Integer.valueOf(Integer.java:582)
    at chess_engine.King.move(King.java:6)
    at chess_engine.MainClass.main(MainClass.java:12)

Thanks in advance!

iK is null and hence you can't parse it. May you want to just declare coordinateKing and move coordinateKing = Integer.valueOf(iK); in the else block ? — Alexis C.
– Alexis C., Commented Jan 14, 2014 at 14:13

Bill the Lizard · Accepted Answer · 2014-01-14 14:23:12Z

2

You're attempting to convert iK to an integer before you check to see if it's null. This line is where the exception is thrown:

Integer coordinateKing = Integer.valueOf(iK);

But you check if (iK == null) on the line following that. You should do a null test first. You can fix this by declaring coordinateKing before your if statement and setting its value in the if...else blocks.

Integer coordinateKing = 0;

if (iK == null){           
    coordinateKing = rand.nextInt(8);
} else {
    coordinateKing = Integer.valueOf(iK);
    int caseI;
    ...
}

edited Jan 14, 2014 at 14:23

answered Jan 14, 2014 at 14:15

Bill the Lizard

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Comments

Nanne · Accepted Answer · 2014-01-14 14:14:03Z

2

You call this

Integer coordinateKing = Integer.valueOf(iK);

but iK can be NULL there. do your null check first

answered Jan 14, 2014 at 14:14

Nanne

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Comments

Kevin Workman · Accepted Answer · 2014-01-14 14:13:51Z

1

The exception is pretty self-explanatory. iK is a null String, which can't be converted to an Integer. What Integer do you want when iK is null?

answered Jan 14, 2014 at 14:13

Kevin Workman

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Muhammad · Accepted Answer · 2014-01-14 14:44:27Z

1

It is a runtime error: here the iK is receiving a null value and an Integer object can store null but the method valueOf() internally uses the parseInt() method which returns an int value and a null cannot be converted to int

answered Jan 14, 2014 at 14:44

Muhammad

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