How to use goto statement correctly

Question

I am taking my high school AP Computer Science class.

I decided to throw a goto statement into a one of our labs just to play around, but I got this er

Answer 1

Java also does not use line numbers, which is a necessity for a GOTO function. Unlike C/C++, Java does not have goto statement, but java supports label. The only place where a label is useful in Java is right before nested loop statements. We can specify label name with break to break out a specific outer loop.

Answer 2

As already pointed out by all the answers goto - a reserved word in Java and is not used in the language.

restart: is called an identifier followed by a colon.

Here are a few things you need to take care of if you wish to achieve similar behavior -

outer:                  // Should be placed exactly before the loop
loopingConstructOne  {  // We can have statements before the outer but not inbetween the label and the loop          
    inner:
    loopingConstructTwo {
        continue;       // This goes to the top of loopingConstructTwo and continue.
        break;          // This breaks out of loopingConstructTwo.
        continue outer; // This goes to the outer label and reenters loopingConstructOne.
        break outer;    // This breaks out of the loopingConstructOne.
        continue inner; // This will behave similar to continue.
        break inner;    // This will behave similar to break.
    }
}

I'm not sure of whether should I say similar as I already have.

Answer 3

If you look up continue and break they accept a "Label". Experiment with that. Goto itself won't work.

public class BreakContinueWithLabel {

    public static void main(String args[]) {

        int[] numbers= new int[]{100,18,21,30};

        //Outer loop checks if number is multiple of 2
        OUTER:  //outer label
        for(int i = 0; i<numbers.length; i++){
            if(i % 2 == 0){
                System.out.println("Odd number: " + i +
                                   ", continue from OUTER label");
                continue OUTER;
            }

            INNER:
            for(int j = 0; j<numbers.length; j++){
                System.out.println("Even number: " + i +
                                   ", break  from INNER label");
                break INNER;
            }
        }      
    }
}

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Answer 4

goto doesn't do anything in Java.

Answer 5

There is not 'goto' in the Java world. The main reason was developers realized that complex codes which had goto would lead to making the code really pathetic and it would be almost impossible to enhance or maintain the code.

However this code could be modified a little and using the concept of continue and break we could make the code work.

    import java.util.*;

public class Factorial 
{
    public static void main(String[] args) 
    {
        int x = 1;
        int factValue = 1;
        Scanner userInput = new Scanner(System.in);
        restart: while(true){
        System.out.println("Please enter a nonzero, nonnegative value to be factorialized.");
        int factInput = userInput.nextInt();

        while(factInput<=0)
        {
            System.out.println("Enter a nonzero, nonnegative value to be factorialized.");
            factInput = userInput.nextInt();
        }

        if(x<1)//This is another way of doing what the above while loop does, I just wanted to have some fun.
        {
            System.out.println("The number you entered is not valid. Please try again.");
            continue restart;
        }
        while(x<=factInput)
        {
            factValue*=x;
            x++;
        }
        System.out.println(factInput+"! = "+factValue);
        userInput.close();
        break restart;
}
    }
}

Answer 6

Java does not support goto, it is reserved as a keyword in case they wanted to add it to a later version