Question

Code:

public class NodeType {

    public int value;
    public NodeType next;

    public NodeType(){
        value = 0;
        next = null;
    }

    public void printFollowingNodesInOrder(){
        System.out.println(this.value);
        while(this.next != null){
            this.next.printFollowingNodesInOrder();
        }
    }
}

Test class:

public class TestClass {

    public static void main(String[] args){

        NodeType nodeOne = new NodeType();
        NodeType nodeTwo = new NodeType();
        NodeType nodeThree = new NodeType();

        nodeOne.value = 1;
        nodeTwo.value = 2;
        nodeThree.value = 3;

        nodeOne.next = nodeTwo;
        nodeTwo.next = nodeThree;

        nodeOne.printFollowingNodesInOrder();       
    }   
}

When I run this main method, the method does not seem to exit after 3.
The output is:
1
2
3
3
3
3
3
3
3

Can anyone see where the problem is?

Answer 1

while (this.next != null)

is looping forever once it starts calling printFollowingNodesInOrder on the final node, because the second to last node (the one where the function is being called) has a next that will never go away. You don’t need to do it in a loop when you’re using recursion to access the next node. Take the loop out and it will work, but be sure to check for null before calling the function.