java - JComponents are not showing up on JPanel -

my jcomponents aren't showing on jpanel reason.

here's code:

main class

import java.awt.color; import java.awt.dimension; import java.awt.graphics; import java.awt.graphics2d;  import javax.swing.jframe; import javax.swing.jpanel;  // main class - executes game  public class main extends jframe {     public static int width = 800, height = 800;     private jpanel jp;     private dimension d;     private snake s;     private food f;      public main()     {         settitle("snake");         setsize(width, height);         setvisible(true);         setdefaultcloseoperation(jframe.exit_on_close);         setlocationrelativeto(null);          d = new dimension(width, height);         jp = new jpanel();         jp.setbackground(color.gray);         jp.setpreferredsize(d);         getcontentpane().add(jp);          // adds snake         s = new snake();         jp.add(s);          // adds food         f = new food();         jp.add(f);     }      @override     public void paint(graphics g)     {         super.paint(g);         graphics2d g2 = (graphics2d) g;     }      public static void main(string args[])     {         new main();     } } 

snake class

import java.awt.color; import java.awt.graphics; import java.awt.graphics2d; import java.awt.event.keyevent; import java.awt.event.keylistener; import java.util.arraylist;  import javax.swing.jcomponent;  // snake class - creates snake object  public class snake extends jcomponent implements keylistener {     public arraylist snakelist = new arraylist();     public int snakex, snakey, snakewidth, snakeheight;      public snake()     {         snakex = 100;         snakey = 100;         snakewidth = 20;         snakeheight = 20;          snakelist.add(1);          addkeylistener(this);     }      @override     public void paintcomponent(graphics g)     {         super.paintcomponent(g);         graphics2d g2 = (graphics2d) g;          g2.setcolor(color.red);         g2.fillrect(snakex, snakey, snakewidth, snakeheight);     }      @override     public void keypressed(keyevent e)     {         if(e.getkeycode() == keyevent.vk_w || e.getkeycode() == keyevent.vk_up)         {             snakex += 10;             system.out.println("up");         }          if(e.getkeycode() == keyevent.vk_s || e.getkeycode() == keyevent.vk_down)         {             snakex -= 10;             system.out.println("down");         }          if(e.getkeycode() == keyevent.vk_d || e.getkeycode() == keyevent.vk_right)         {             snakey += 10;             system.out.println("right");         }          if(e.getkeycode() == keyevent.vk_a || e.getkeycode() == keyevent.vk_left)         {             snakey -= 10;             system.out.println("left");         }     }      @override     public void keyreleased(keyevent e)     {      }      @override     public void keytyped(keyevent e)     {}   } 

food class

import java.awt.color; import java.awt.graphics; import java.awt.graphics2d; import java.util.random;  import javax.swing.jcomponent; import javax.swing.jpanel;  // food class - class adds more snake objects when collided snake  public class food extends jcomponent {     private random r = new random();     public int foodx, foody, foodwidth = 20, foodheight = 20;      public food()     {         foodx = 400;         foody = 400;     }      @override     public void paintcomponent(graphics g)     {         super.paintcomponent(g);         graphics2d g2 = (graphics2d) g;          g2.setcolor(color.yellow);         g2.fillrect(foodx, foody, foodwidth, foodheight);     } } 

as can see, have 3 classes: 2 jcomponents , 1 jframe (my main class).

the main class has jpanel within added jframe, , jpanel adds both 2 jcomponents reason jcomponents not showing when execute though i'm pretty sure have done correctly.

if knows why not working that'd awesome. thanks!

your food jcomponent's preferred size 0,0, , size preferentially take. 1 simple solution either set preferred size or override getpreferredsize() method, think if might expose bigger problem program. assume want display snake , food in same screen space. if so, you're program structure wrong -- food , snake classes should not component classes (e.g., shouldn't extend jpanel or jcomponent) rather should logical classes. should have 1 jpanel drawing has paintcomponent overridden , inside method paints snakes , food.

a side bit: you're overriding jframe's paint method, dangerous thing do. fortunately you're doing harm in currently, presence might tempt later draw in there. don't. recommend remove method , temptation. own preference never extend jframe there reason this, , risks doing so.

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regarding comments:

to make clear, you're saying have 1 paintcomponent() in main

i don't know "main" is. mentioned above, create 1 jpanel painting, override protected void paintcomponent(graphics g) method, , paint snake , food within method.

and not in either snake or food class?

correct. snake , food should not extend swing component , therefore should not override paintcomponent. give them public void draw(graphics g) method called in above class's paintcomponent method , passes in graphics or graphics2d object given jvm.

and also, i'll make main extend jpanel instead of jframe. if that's case, create snake , food objects in main class?

these details depend on actual code. i'm confident you'll figure out.

and also, can keep keylistener in snake class or should put in main class?

i never use keylisteners , instead favor key bindings. @ many posts on subject, many example code more.