box2d working properly

box2dproper.java

package com.example.libgdx.skeleton;

import com.badlogic.gdx.ApplicationListener;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.graphics.GL10;
import com.badlogic.gdx.graphics.OrthographicCamera;
import com.badlogic.gdx.math.Matrix4;
import com.badlogic.gdx.math.Rectangle;
import com.badlogic.gdx.math.Vector2;
import com.badlogic.gdx.physics.box2d.*;


public class SkeletonMain implements ApplicationListener {
	World world ;
	Box2DDebugRenderer debugRenderer;
	OrthographicCamera camera;
	static final float BOX_STEP=1/60f;
	static final int BOX_VELOCITY_ITERATIONS=8;
	static final int BOX_POSITION_ITERATIONS=3;
	static final float WORLD_TO_BOX=0.01f;
	static final float BOX_WORLD_TO=100f;
	Rectangle ball;
	Body body;

	@Override
	public void create() {
		world = new World(new Vector2(0, -100), true);
		camera = new OrthographicCamera();

		camera.viewportHeight = 480;
		camera.viewportWidth = 800;
		camera.position.set(camera.viewportWidth * .5f, camera.viewportHeight * .5f, 0f);
		camera.zoom = 1f;
		camera.update();

		//Ground body
		BodyDef groundBodyDef =new BodyDef();
		groundBodyDef.position.set(new Vector2(0, 10 * WORLD_TO_BOX));
		Body groundBody = world.createBody(groundBodyDef);
		PolygonShape groundBox = new PolygonShape();
		float w = (camera.viewportWidth * 2) * WORLD_TO_BOX;
		float h = 10.0f * WORLD_TO_BOX;
		groundBox.setAsBox(w, h);
		groundBody.createFixture(groundBox, 0.0f);

		//Dynamic Body
		BodyDef bodyDef = new BodyDef();
		bodyDef.type = BodyDef.BodyType.DynamicBody;
		float posX = (camera.viewportWidth / 8) * WORLD_TO_BOX;
		float posY = (camera.viewportHeight / 2) * WORLD_TO_BOX;
		bodyDef.position.set(posX, posY);
		body = world.createBody(bodyDef);

		// create a Rectangle to logically represent the ball
		CircleShape dynamicCircle = new CircleShape();
		float radius = 40f * WORLD_TO_BOX;
		dynamicCircle.setRadius(radius);
		FixtureDef fixtureDef = new FixtureDef();
		fixtureDef.shape = dynamicCircle;
		fixtureDef.density = 1.0f;
		fixtureDef.friction = 0.0f;
		fixtureDef.restitution = 0.7f;
		body.createFixture(fixtureDef);
		debugRenderer = new Box2DDebugRenderer();

		listener listener1=new listener();
		world.setContactListener(listener1);
	}

	private static Matrix4 debugProjection = new Matrix4();

	@Override
	public void render() {
		Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
		debugProjection.set(camera.combined);
		debugProjection.scl(BOX_WORLD_TO);
		debugRenderer.render(world, debugProjection);
		world.step(BOX_STEP, BOX_VELOCITY_ITERATIONS, BOX_POSITION_ITERATIONS);
	}
	class listener implements ContactListener
	{

		@Override
		public void beginContact(Contact contact) {
			// TODO Auto-generated method stub

		}

		@Override
		public void endContact(Contact contact) {
			// TODO Auto-generated method stub
			body.applyLinearImpulse(0, 2f, body.getWorldCenter().x, body.getWorldCenter().y, true);
			//body.setLinearVelocity(0,50000000);
			System.out.println("Collision detected");
		}

		@Override
		public void preSolve(Contact contact, Manifold oldManifold) {
			// TODO Auto-generated method stub

		}

		@Override
		public void postSolve(Contact contact, ContactImpulse impulse) {
			// TODO Auto-generated method stub

		}

	};

	@Override
	public void resize(int width, int height) {
	}
	@Override
	public void pause() {
	}
	@Override
	public void resume() {
	}
	@Override
	public void dispose() {
	}
}