Question

I am trying some code but I cannot compile it. is there any error? I have attached the code below.

import java.util.*;
import java.io.*;
import javax.swing.*;
import java.awt.event.*;

public class Node
{
  private int nodeId;
  private List<Connection> outboundConnections = new ArrayList<>();

  public Node(int nodeId)
  {
    this.nodeId = nodeId;
  }

  public void addConnection(Connection connection)
  {
    this.outboundConnections.add(connection);
  }
}

and when i compile, i got this kind of error :

Node.java:9: error: cannot find symbol

  private List<Connection> outboundConnections = new ArrayList<>();

               ^
  symbol:   class Connection

  location: class Node

Node.java:16: error: cannot find symbol

  public void addConnection(Connection connection)
                            ^
  symbol:   class Connection

  location: class Node

Node.java:9: error: unexpected type

  private List<Connection> outboundConnections = new ArrayList<>();

                                                              ^
  required: class

  found:    <E>ArrayList<E>

  where E is a type-variable:

    E extends Object declared in class ArrayList

3 errors

Answer 1

private List<Connection> outboundConnections = new ArrayList<>();

is only valid on Java 7+. If you run Java 6 or earlier, you need to use:

private List<Connection> outboundConnections = new ArrayList<Connection>();