Shader

package net.lesson.graphics.shaders;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import org.lwjgl.opengl.*;
import org.lwjgl.opengl.GL20;

public abstract class Shader {

    private int programID;
    private int vertexShaderID;
    private int fragmentShaderID;

    public Shader(String vertexFile, String fragmentFile){
        vertexShaderID =loadShader(vertexFile,GL20.GL_VERTEX_SHADER);
        fragmentShaderID =loadShader(fragmentFile,GL20.GL_FRAGMENT_SHADER);
        programID = GL20.glCreateProgram();
        GL20.glAttachShader(programID, vertexShaderID);
        GL20.glAttachShader(programID, fragmentShaderID);

        GL20.glLinkProgram(programID);
        GL20.glValidateProgram(programID);
        bindAttributes(vertexShaderID, vertexFile);
        bindAttributes(fragmentShaderID, fragmentFile);
    }


    protected void bindAttributes(int attribute, String varibaleName){

        GL20.glBindAttribLocation(programID, attribute, varibaleName);
    }

public void start(){
    GL20.glUseProgram(programID);
}
    public void stop(){
        GL20.glUseProgram(0);
    }
    public void cleanUp(){
        stop();
        GL20.glDetachShader(programID, vertexShaderID);
        GL20.glDetachShader(programID, fragmentShaderID);
        GL20.glDeleteShader(vertexShaderID);
        GL20.glDeleteShader(fragmentShaderID);
        GL20.glDeleteProgram(programID);
    }
    private static int loadShader(String file, int type){
        StringBuilder shaderSource = new StringBuilder();
        try{
            BufferedReader reader = new BufferedReader(new FileReader(file));
            String line;
            while((line = reader.readLine())!=null){
        shaderSource.append(line).append("\n");
            }
            reader.close();
            }catch(IOException ex){
                System.err.println("Could not read file");
                ex.printStackTrace();
                System.exit(-1);
        }
        int shaderID = GL20.glCreateShader(type);
        GL20.glShaderSource(shaderID, shaderSource);
        GL20.glCompileShader(shaderID);
        if(GL20.glGetShaderi(shaderID, GL20.GL_COMPILE_STATUS)==GL11.GL_FALSE){
            System.out.println(GL20.glGetShaderInfoLog(shaderID, 500));
            System.err.println("Could not compile");
            System.exit(-1);
        }
        return shaderID;

    }
}