Node

Examine the following Java class:

// Node.java
//
public class Node
{
  private int  value;
  private Node next;
  
  // Constructor. Make a Node containing val.
  // Initialize next to null
  public Node ( int val )
  {
    value = val;
    next = null;
  }
  
  public int  getValue() { return value; }  // get the value in this Node
  public Node getNext()  { return next; }   // get a pointer to another Node
  
  public void setValue( int val ) { value = val; }
  public void setNext( Node nxt ) { next = nxt; } 
  
  public String toString() { return "" + value; } // return a string based on value
}

Recall that + means string concatenation. String concatenation automatically uses the toString() method of the object.

Here is a program that tests the class:

// NodeTester.java
//
public class NodeTester
{
  public static void main ( String[] args )
  {
    Node node0 = new Node( 223 );  
    System.out.println("Node 0: " + node0 );
  }
}

The program constructs a Node object and puts a reference to in in node0. The member next is of type Node (a potential reference to another Node object). The slash in next represents the null put there by the constructor. So to start, it points to no object.

Compile and run the program:

C:\JavaSource> javac Node.java NodeTester.java
C:\JavaSource> java  NodeTester
Node 0: 223
C:\JavaSource>

public class NodeTester
{
  public static void main ( String[] args )
  {
    Node node0 = new Node( 223 );  
    System.out.println("Node 0: " + node0 );

    node0.setValue( 17 ); 
    System.out.println("new value: " + node0 );
  }
}