Bug 666 - NullPointerException on snakemove field in UIPainting.java after refactoring
Summary: NullPointerException on snakemove field in UIPainting.java after refactoring
Status: RESOLVED FIXED
Alias: None
Product: CS3343 2021/22 Group16 Greedy Snake
Classification: Unclassified
Component: Action Package (show other bugs)
Version: Ver 3.0
Hardware: PC Windows
: --- critical
Assignee: Baron Qu
URL:
Depends on:
Blocks:
 
Reported: 2021-12-06 17:57 HKT by WANG Yiwen
Modified: 2021-12-06 18:06 HKT (History)
1 user (show)

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Description WANG Yiwen 2021-12-06 17:57:05 HKT 
There is a NullPointerException occurs on the new snakemove field after you performed refactoring.

Steps to reproduce:
1. Run Main.java
2. Press key 1/2 to choose a mode.

Expected Output:
No error

Actual Output:
The below error message is shown in the console
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException: Cannot invoke "com.cs3343_Group16.greedySnake.service.SnakeMove.move(com.cs3343_Group16.greedySnake.model.Snake)" because "this.snakemove" is null
	at com.cs3343_Group16.greedySnake.action.UIPainting.actionPerformed(UIPainting.java:94)
	at java.desktop/javax.swing.Timer.fireActionPerformed(Timer.java:311)
	at java.desktop/javax.swing.Timer$DoPostEvent.run(Timer.java:243)
	at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:318)
	at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:771)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:722)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:716)
	at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
	at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:741)
	at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
	at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
Comment 1 LI Ruoxin 2021-12-06 18:05:35 HKT 
The bug is due to we forgot to consider the situation where the snakemove field is not yet set.

The below modification is done and the game now woks well.

//modified actionPerformed in UIPainting.java
public void actionPerformed(ActionEvent e) {
		keyLock = SConstant.SC_UPDATED_KEYBOARD_LOCK;
		timer.start();
		if (!SConstant.SC_GAME_MODE_DEFAULT.equals(game.getMode())) {
			if (SConstant.SC_GAME_MODE_AI.equals(game.getMode())) {
				MapStatement.getInstance().initRecord();
				game.getSnake().updateMapStatus();
				game.getBean().updateMapStatus();
				game.getSnake().setDirection(SnakeSelfAutoMove.thinkAndMove(((AISnake) game.getSnake()), game.getBean(),
						game.getSnake().getDirection()));
			}
			
			setSnakemove(game.getSnake().getDirection());
			if(snakemove!=null) { // This if else statement is added
				snakemove.move(game.getSnake());
			}		
		}

		repaint();
	}