How to resolve NullPointerException?

Question

I am trying to create a JPanel that asks whether the player wants to hit or stand in a Black Jack game.

public class decisionLayout extends JFrame
{
JPanel decisionPanel; 

public JButton buttons[];

private final String names[] = { "YES", "NO" };

final static String ASK_FOR_DECISION = "Decide whether to hit or not.";

public decisionLayout() 
{ 
    super( "decisionPanel demo" ); 

    JPanel panel = new JPanel();
    JPanel TextFieldPanel = new JPanel(); 
    final JTextField tf = new JTextField(); 
    tf.setText( ASK_FOR_DECISION ); 

    tf.setEditable( false );  
    TextFieldPanel.add( tf );

    // create the decisions 
    JPanel decisionPlace = new JPanel(); 

    for ( int count = 0; count < buttons.length; count++ )
    { 
        buttons[ count ] = new JButton( names[ count ] ); 
        buttons[ count ].addActionListener( 
            new ActionListener() 
            { 
                public void actionPerformed( ActionEvent e )
                { 
                    if( e.getSource() == buttons[ 0 ] )
                    { 
                        tf.setText( "Yes. You want more cards." );
                    }
                    else
                    { 
                        tf.setText( "No. You do not want more cards." );
                    }
                }
            }
        );
    }

    JPanel decisionPanel = new JPanel(); 
    decisionPanel.add( decisionPlace );

    panel.add( TextFieldPanel, BorderLayout.PAGE_START ); 
    panel.add( decisionPanel, BorderLayout.CENTER );
}

} `

I do not see why there is a compilation error at line:

 for ( int count = 0; count < buttons.length; count++ )

,which is what eclipse keeps telling me. Does anybody have any ideas why this is happening?

Compilation error or runtime `NullPointerException`? – Sotirios Delimanolis Mar 16 '15 at 15:22 — Sotirios Delimanolis, Mar 16 '15 at 15:22
You never initialize `buttons[]` array – brso05 Mar 16 '15 at 15:23 — brso05, Mar 16 '15 at 15:23

score 1 · Answer 1 · answered Mar 16 '15 at 15:24

1

public JButton buttons[];

You never initialize your buttons, so when you try to call buttons.length you get an NPE. You probably want to actually place some buttons in that array

answered Mar 16 '15 at 15:24

Dragondraikk

1,659
11
21

score 1 · Answer 2 · answered Mar 16 '15 at 15:24

1

You never initialize the buttons[]. buttons[] has no length:

for ( int count = 0; count < **buttons.length**; count++ )

answered Mar 16 '15 at 15:24

brso05

13,142
2
21
40

How to resolve NullPointerException?

2 Answers2