java - AWT-Exception NullPointer when Accessing Another Class -

i have 2 classes, drawsnakegamepanel , maze. trying call method in maze class in drawsnakegamepanel class. think have maze class initiated, each time triggers nullpointererror. don't understand null it's referring to. obvious don't it. help.

public class drawsnakegamepanel extends jpanel {  private snake snake; private kibble kibble; private score score; private maze maze;  drawsnakegamepanel(snake s, kibble k, score sc){     this.snake = s;     this.kibble = k;     this.score = sc;  public void paintcomponent(graphics g) {     super.paintcomponent(g);             switch (gamestage) {      case 2 : {         displaygame(g);  //exception here         break;  }  private void displaygame(graphics g) {     displaygamegrid(g);     displaysnake(g);     displaykibble(g);     maze.displaymaze(g);  //breaks here   } }  public class maze extends jpanel {  int xnumofsquares = (501 / 30); int ynumofsquares = (501/30); int squaresize = 30;  public maze(int maxx, int maxy, int squaresize){     this.xnumofsquares = maxx;     this.ynumofsquares = maxy;     this.squaresize = squaresize; }  public void displaymaze(graphics g){     g.fillrect(30,30,squaresize,squaresize);     g.fillrect(30,60,squaresize,squaresize);     g.fillrect(30,90,squaresize,squaresize);  } } 

error stack:

exception in thread "awt-eventqueue-0" java.lang.nullpointerexception @ com.marty.drawsnakegamepanel.displaygame(drawsnakegamepanel.java:118) @ com.marty.drawsnakegamepanel.paintcomponent(drawsnakegamepanel.java:66) @ javax.swing.jcomponent.paint(jcomponent.java:1054) @ javax.swing.jcomponent.painttooffscreen(jcomponent.java:5222) @ javax.swing.repaintmanager$paintmanager.paintdoublebuffered(repaintmanager.java:1572) @ javax.swing.repaintmanager$paintmanager.paint(repaintmanager.java:1495) @ javax.swing.repaintmanager.paint(repaintmanager.java:1265) @ javax.swing.jcomponent._paintimmediately(jcomponent.java:5170) @ javax.swing.jcomponent.paintimmediately(jcomponent.java:4981) @ javax.swing.repaintmanager$4.run(repaintmanager.java:824) @ javax.swing.repaintmanager$4.run(repaintmanager.java:807) @ java.security.accesscontroller.doprivileged(native method) @ java.security.protectiondomain$1.dointersectionprivilege(protectiondomain.java:75) @ javax.swing.repaintmanager.paintdirtyregions(repaintmanager.java:807) @ javax.swing.repaintmanager.paintdirtyregions(repaintmanager.java:782) 

you didn't assign value maze. need (the numbers arbitrary):

private maze maze = new maze(3, 3 , 5);