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Thread: can't compare class fields

  1. #1
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    Default can't compare class fields

    hi ! There two classes
    Node.java
    DataPacket.java
    The problem is I can't compare the field of the passed object "dp" with the field of the stored dataPacket, data packets are stored in the ArrayList "dataPackets". At the end I add also the full code for the Node class.

    the Node.java contains the following method
    public void acceptDPacket(DataPacket dp){
    		boolean packetHere;
    		for (int j = 0; j < dataPackets.size(); j++) {
    			if (dp.getSeqNo() = dataPackets[j].getSeqNo()){
    				packetHere = true;
    				break;
    			}
    		}
    		if (packetHere = true){
     
    		} else dataPackets.add(dp);
    	}

    public class DataPacket {
     
    	private Node dest;
    	private Node source;
    	private int seqNo;
    	private String content;
     
    	public DataPacket(String cont, Node dest, Node src) {
    		this.content = cont;
    		this.dest = dest;
    		this.source = src;
     
    	}
     
    	public int getSeqNo(){
    		return seqNo;
    	}
     
    	public String getContent(){
    		return content;
    	}
     
    }

    import java.util.ArrayList;
     
    public class Node extends Thread{
     
    	// constants initialization
    	final int MAP_LENGTH = 1000;
    	final int MAP_WIDTH = 1000;
     
    	private int x = 0;
    	private int y = 0;
    	private int node_id;
    	ArrayList<DataPacket> dataPackets = new ArrayList<DataPacket>();
     
    	//node_id = thread's name
    	public Node(String node_id) {
    		super(node_id);
    		this.x = (int) (MAP_LENGTH * Math.random());
    		this.y = (int) (MAP_WIDTH * Math.random());
    	}
     
    	public void run(){
    		System.out.println("Inside of node"+getNodeId()+" thread!");
    	}
     
    	public int getX() {
    		return x;
    	}
     
    	public void setX(int x) {
    		this.x = x;
    	}
     
    	public int getY() {
    		return y;
    	}
     
    	public void setY(int y) {
    		this.y = y;
    	}
     
    	public int getNodeId() {
    		return this.node_id;
    	}
     
    	public void setNodeId(int nid){
    		this.node_id = nid;
    	}
     
    	public void acceptDPacket(DataPacket dp){
    		boolean packetHere;
    		for (int j = 0; j < dataPackets.size(); j++) {
    			if (dp.getSeqNo() = dataPackets[j].getSeqNo()){
    				packetHere = true;
    				break;
    			}
    		}
    		if (packetHere = true){
     
    		} else dataPackets.add(dp);
    	}
     
    }
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    Last edited by r0x; November 26th, 2011 at 04:32 PM.


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: can't compare class fields

    I can't compare the field of the passed object "dp" with the field of the stored dataPacket,
    If you get errors, please post the full text of the error message.

    Make sure your testing for equality uses the correct operator: ==
    I see what looks like an assignment operator(=) in your code

  3. #3
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    Default Re: can't compare class fields

    thanks for the reply!! the problem was also in accessing elements of the ArrayList, I forgot that there is a method get()

    if (dp.getSeqNo() == dataPackets.get(j).getSeqNo())

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