Custom Collisions

Newbie & Debugging Questions
#1

for the longest time I have been using just rectangles to handle collision, and I was happy with that but I wanted to branch out in to something more complex with polygons using slick2d as the base system.

after some working with it I realized how easy is was compared to what I was doing before, but I ran into a problem. What I want is the ability to slide up slopes with little to no customization of the engine to handle certain shapes.

this is the basis of what I have so far

Entity.class

package Pheniox.Entity;

import java.util.ArrayList;

import org.newdawn.slick.GameContainer;
import org.newdawn.slick.Graphics;
import org.newdawn.slick.geom.Shape;
import org.newdawn.slick.geom.Vector2f;
import org.newdawn.slick.state.StateBasedGame;

import Pheniox.World.World;

public abstract class Entity {
	protected Vector2f position = new Vector2f(0,0);
	protected Vector2f velocity = new Vector2f(0,0);
	protected World world;
	public boolean removed = false;
	private Object entities;
	
	//collision booleans
	protected boolean collideTop,collideLeft, collideBottom,collideRight;
	
	//constructors

	public Entity(float x, float y){
		position.x = x;
		position.y = y;
	}
	
	public void init(World world){
		this.world = world;
		init();
	}
	//removes the player from the world
	public void remove(){
		removed = true;
	}
	
	//Movement methods
	public void move(Vector2f vel, int delta){
		move(vel.x, vel.y, delta);
	}
	//takes 2 floats and moves
	public void move(float xa, float ya, int delta){
		if(xa != 0 && ya != 0){
			move(xa, 0,delta);
			move(0,ya,delta);
			return;
		}
		
		boolean canPass = true;
		
		collideTop = false;
		collideLeft = false;
		collideBottom = false;
		collideRight = false;
		
		
		ArrayList<Entity> entities = world.getEntities();
		
		for(Entity e: entities){
			if(e != this){
				if(this.getCollisionBox(xa * delta, ya * delta).intersects(e.getCollisionBox(e.velocity.x * delta,e.velocity.y * delta))){
					canPass = false;
				
			
		}
		if(xa > 0 && !canPass){
			collideLeft = true;
		}
		if(xa < 0 && !canPass){
			collideRight = true;
		}
		if(ya > 0 && !canPass){
			collideBottom = true;
		}
		if(ya < 0 && !canPass){
			collideTop = true;
		}
	}
}
		
		
		
		if(canPass){
		this.position.x += delta * xa;
		this.position.y += delta * ya;
		}
		
	}
	//render methods
	public void render(GameContainer gc, Graphics g){
		renderEntity(gc,g);
	}
	//update methods
	public void update(GameContainer gc, StateBasedGame sbg , int delta){
		move(velocity.x,velocity.y,delta);
		updateEntity(gc,sbg,delta);
	}
	
	//abstract classes
	public abstract void init();
	public abstract void renderEntity(GameContainer gc,Graphics g);
	public abstract void updateEntity(GameContainer gc, StateBasedGame sbg, int delta);
	public abstract Shape getCollisionBox(float xa, float ya);
}

the collision box shape is declared in “getCollisionBox(float xa, float ya)”
when being extends by other classes

basicaly what I want is say in a 2d platformer the ability to go up slopes, and I want it to just inheret to the entity class and not have certain cases that make it happen.

any help would be appreciated.