Debugging with Eclipse: A Quick Introduction

--D. Thiebaut (talk) 10:44, 22 October 2014 (EDT)

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This is a short tutorial on how to get started with the Eclipse Debugger. Mastering the debugger takes time. The purpose of this lab/tutorial is just to show you how to get started.

Getting Started

• Open Eclipse
• Create a New Java Class. Call it DebugDemo.
• Enter this code in it:

// DebugDemo.java
// D. Thiebaut
// CSC212
import java.util.ArrayList;
import java.util.Iterator;

class Pair {
	public String name;
	public int age;
	Pair( String f, int s ) { name=f; age=s; }
	public String toString() { return name+"("+age+") "; }
}

public class DebugDemo {
	
	
	public static void main(String[] args) {
                ArrayList<Pair> A = new ArrayList<Pair>();
		int increment = 3;
		
		A.add( new Pair( "Alice", 10 ) );
		A.add( new Pair( "Bob", 7 ) );
		
		Iterator<Pair> it = A.iterator();
		while ( it.hasNext() ) {
			Pair p = it.next();
			p.age += increment;
		}
		
		for ( int i=0; i<3; i++ ) {
			Pair p = A.get(  i );
			System.out.println( A.get( i ) );
		}
	}

}

• Run it.
• Observe what the program does. It simply creates an array of 2 pairs, containing Alice(10) and Bob(7), and modify the age of both by an increment of 3.

Debugging DebugDemo

• In the Package Explorer tab (left tab), right/control click on DebugDemo and select Debug As and Java Application.
• The windows will reorganize themselves (if not, see below):

• If you do not get the window shown above, click on the little "table and plus symbol" in the top right of the window, and pick Debug in the new pop-up window :

• You can switch back and forth between Java coding and debugging using the Java and Debug buttons in the top right of the Eclipse window.