Java LWJGL制作简单形状的问题：“在当前线程中找不到OpenGL上下文”

我只是想在窗户上画几个形状。在其他问题中，我现在遇到的最大问题是，在过去几个小时里，我一直试图纠正这个令人恼火的错误：

Exception in thread "main" java.lang.RuntimeException: No OpenGL context found in the current thread.
    at org.lwjgl.opengl.GLContext.getCapabilities(GLContext.java:124)
    at org.lwjgl.opengl.GL11.glEnd(GL11.java:689)
    at project1.project1.process(project1.java:71)
    at project1.project1.main(project1.java:22)
Java Result: 1
BUILD SUCCESSFUL (total time: 0 seconds)

我刚刚开始使用LWJGL和openGL，所以我并不奇怪会出现错误。我也有圆和线算法的问题，但在我开始圆方法之前，程序实际上是在一个窗口中绘制多条线，我仍然只得到带有负斜率的任何线的水平线，但这可能是一个算法问题

package project1;
import java.io.*;
import java.util.*;
import org.lwjgl.opengl.Display;
import org.lwjgl.opengl.DisplayMode;
import static org.lwjgl.opengl.GL11.*;
import static org.lwjgl.opengl.GLContext.*;
import static org.lwjgl.opengl.GL30.*;
import static java.lang.Math.PI;
import org.lwjgl.opengl.GLContext;

public class project1 {
    private ArrayList<String> shapeList = new ArrayList();
    public static void main(String[]args){
        project1 shapes = new project1();
        shapes.readFile();
        shapes.process();
    }
    public void readFile(){
        try(BufferedReader br = new BufferedReader(new FileReader("coordinates.txt"))){
            String line = br.readLine();
            shapeList.add(line);

            int n = 1;
            while( line != null){
                line = br.readLine();
                if(line== null)
                    break;
                shapeList.add(line);
                //System.out.println(line);
                n++;
            }
        }catch(Exception e){
            System.out.println(e);
        }
    }
    public void process(){
        start();

        while(!Display.isCloseRequested()){
            try{
                glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
                glLoadIdentity();               
                glPointSize(10);         
                glBegin(GL_POINTS);

                for(String s: shapeList){
                    char ch = s.charAt(0);
                    switch(ch){
                    //lines
                        case 'l':
                           glColor3f(1.0f,0.0f,0.0f);
                           line(s);
                    //circle
                        case 'c':
                            glColor3f(0.0f,0.0f,1.0f);
                            circle(s);//if you comment this line out, program still makes lines
                    //ellipse
                        case 'e':
                            ellipse(s);
                    }
                }
            }catch(Exception e){
                Display.destroy();
            }         
            glEnd();                
            Display.update();
            Display.sync(60);
        }            
    }
    public void start(){
        try{
            createWindow();
            initGL();
        }catch(Exception e){
            e.printStackTrace();
        }
    }
    public void createWindow() throws Exception{
        Display.setFullscreen(false);
        Display.setTitle("Testing123");
        Display.setDisplayMode(new DisplayMode(640,480));
        Display.create();
        //GLContext.loadOpenGLLibrary();
    }
    public void initGL(){
        glClearColor(0.0f,0.0f,0.0f,0.0f);
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        glOrtho(0, 640, 0, 480, 1, -1);
        glMatrixMode(GL_MODELVIEW);
        glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
    }
    public void line(String s){
        int[] points = new int[4];
        //split into 2 strings by whitespace
        String[] arr = s.split("\\s+");
        //get first coordinate
        String[] first = arr[1].split(",");

        ///get second coordinate
        String[] second = arr[2].split(",");

        int x1 = Integer.parseInt(first[0]);
        int y1 = Integer.parseInt(first[1]);
        int x2 = Integer.parseInt(second[0]);
        int y2 = Integer.parseInt(second[1]);        

        drawLine(x1,y1,x2,y2);
    }
    public boolean drawLine(int x0, int y0, int x1, int y1){
        //System.out.println(x0 + " " + y0 + " " + x1 + " " + y1);
        x0 = 10;
        y0 = 100;
        x1 = 100;
        y1 = 10;
        /**while(!Display.isCloseRequested()){
           try{
                glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
                glLoadIdentity();

                glColor3f(1.0f,0.0f,0.0f);
                glPointSize(10);

                glBegin(GL_POINTS);
                //glVertex2f(350.0f,150.0f);
                //glVertex2f(50.0f,50.0f);
                **/
                //change in y
                int dx = x1 - x0;
                //change in x
                int dy = y1 - y0;

                //distance to midpoint
                //int d = 2*(dy) - dx;
                int d = (dy-dx)/2;
                System.out.println(d);
                //int incrementRight = 2*(dy);
                //int incrementUpRight = 2*(dy-dx);

                //int x = x0, y=y0;
                int y = y0;
                //for(int i=0;x<x1;i++){
                for (int x = x0;x<=x1;x++){
                    if(d>=0){
                        //x = x + 1;
                        y = y + 1;
                        //glVertex2f(x,y);
                        d = dy-dx;
                        //d = d+incrementUpRight;
                    }
                    else{
                        //x = x+1;
                        //y = y+0;
                        //glVertex2f(x,y);
                        d = d+dy;
                        //d = d+incrementRight;
                    }
                    glVertex2f(x,y);
                }   

                //glEnd();

                //Display.update();
                //Display.sync(60);
            //}catch(Exception e){
                //System.out.println("Exception occured");
                //Display.destroy();
            //} 

       // }      
        return true;
    }
    public void circle(String s){
        int[] points = new int[3];
        //split into 2 strings by whitespace
        String[] arr = s.split("\\s+");
        //get first coordinate
        String[] first = arr[1].split(",");

        int x = Integer.parseInt(first[0]);
        int y = Integer.parseInt(first[1]);
        int rad = Integer.parseInt(arr[2]);

        drawCircle(x,y,rad);
    }
    public boolean drawCircle(float radx, float rady, float rad){
        /**        
        int x = 0, y = 0;
        int numSeg = 100;
        //from theta to 2pi
        // x = x+rcostheta;
        // y = y+rsintheta;
        System.out.println("test");
        for(int i = 0;i<numSeg;i++){
            float theta = (float)(2*Math.PI*(float)i)/(float)numSeg;
            double cx = rad*Math.cos(theta);
            double cy = rad*Math.sin(theta);

            glVertex2f((float)cx + x0,(float)cy + y0);
        }
        **/
        float x = 0;
        float y = rad;
        float d = (5 - rad*4)/4;
        glVertex2f(112,400);
        System.out.println(y);
        /**
        do{
            glVertex2f( radx+x, rady+y);
            glVertex2f( radx+x, rady-y);
            glVertex2f(radx-x, rady+y);
            glVertex2f(radx-x, rady-y);
            glVertex2f(radx+x, rady+x);
            glVertex2f(radx+x, rady-x);
            glVertex2f(radx-y, rady+x);
            glVertex2f(radx-y, rady-x);

            if(d<0){
                d += 2*x +1;
            }else{
                d += 2*(x-y)+1;
                y--;
            }
            x++;
        }while(x<=y);**/

        return true;
    }

    public void ellipse(String s){

    }

}

c是圆，e是椭圆，l是线。。 格式化/解析工作正常。我正在研究算法，我真的只是想知道为什么会发生这种错误？我不明白这个错误已经有好几个小时了，我快疯了。为什么圆的方法不起作用，而直线却起作用？

好吧。 万一有人还在想办法。。。 我忘了我的休息声明了..>_

c 320,100 54
e 100,100 45,80
l 10,380 380,10
l 350,50 500,70
e 450,250 75,35
c 50,50 100