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Thread: "java.lang.NoSuchMethodError: main" and "fatal exception occured."

  1. #1
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    Default "java.lang.NoSuchMethodError: main" and "fatal exception occured."

    This code gives me those error messages when I run it.


    import java.awt.FlowLayout;
    import java.awt.event.ActionListener;
    import java.awt.event.ActionEvent;
    import javax.swing.JFrame;
    import javax.swing.JTextField;
    import javax.swing.JButton;
    import javax.swing.JLabel;
     
    public class TempConverter extends JFrame{
     
    	private JButton button1;
    	private JButton button2;
    	private JTextField field1;
    	private JLabel label1;
    	String input = field1.getText();
    	String string = "";
    	public TempConverter(){
    		super("Temperature converter");
    		setLayout(new FlowLayout());
     
     
     
    		button1 = new JButton("C to F");
    		add(button1);
    		button2 = new JButton("F to C");
    		add(button2);
    		field1 = new JTextField(5);
    		add(field1);
    		String input = field1.getText();
     
    		label1 = new JLabel(string);
    		add(label1);
     
    		EventHandler handler = new EventHandler();
    		button1.addActionListener(handler);
    		button2.addActionListener(handler);
     
    	}
     
    	public class EventHandler implements ActionListener{
     
    		public void actionPerformed(ActionEvent event){
     
    			try{
    			if(event.getSource() == button1)
    				string =  Double.toString((Double.parseDouble(input) - 32) * 5 / 9);
     
    			if(event.getSource() == button2)
    				string = Double.toString(Double.parseDouble(input) * 9 / 5 + 32);
    			}
    			catch(NumberFormatException exception){
    				string = "ERROR";
    			}
    		}
     
    	public void main(String [] args){
     
    		TempConverter bucky = new TempConverter();
    		bucky.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    		bucky.setSize(400,80);
    		bucky.setVisible(true);
    	}
    }
    }


  2. #2
    Java kindergarten chronoz13's Avatar
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    Default Re: "java.lang.NoSuchMethodError: main" and "fatal exception occured."

    your main method doesnt have static modifier, and also your main method is inside the inner class.

  3. #3
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    Default Re: "java.lang.NoSuchMethodError: main" and "fatal exception occured."

    I've put the static modifier in front of the main method now, and I think it's outside the inner class..
    Still I get: "Exception in thread "main" java.lang.NullPointerException
    at TempConverter.<init>(TempConverter.java:15)
    at TempConverter.main(TempConverter.java:40)"
    When I run it.

    I skipped all the import statements this time.

    import java.awt.FlowLayout;
     
    public class TempConverter extends JFrame{
     
    	private JButton button1;
    	private JButton button2;
    	private JTextField field1;
    	private JLabel label1;
    	String input = field1.getText();
    	String string = "";
     
    	public TempConverter(){
    		super("Temperature converter");
     
    		setLayout(new FlowLayout());
    		button1 = new JButton("C to F");
    		add(button1);
    		button2 = new JButton("F to C");
    		add(button2);
    		field1 = new JTextField(5);
    		add(field1);
    		String input = field1.getText();
     
    		label1 = new JLabel(string);
    		add(label1);
     
    		EventHandler handler = new EventHandler();
    		button1.addActionListener(handler);
    		button2.addActionListener(handler);
     
    	}
     
    	public static void main(String [] args){
    		TempConverter bucky = new TempConverter();
    		bucky.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    		bucky.setSize(400,80);
    		bucky.setVisible(true);
    	}
     
     
     
     
     
     
    	public class EventHandler implements ActionListener{
     
    		public void actionPerformed(ActionEvent event){
     
    			try{
    			if(event.getSource() == button1)
    				string =  Double.toString((Double.parseDouble(input) - 32) * 5 / 9);
     
    			if(event.getSource() == button2)
    				string = Double.toString(Double.parseDouble(input) * 9 / 5 + 32);
    			}
    			catch(NumberFormatException exception){
    				string = "ERROR";
    			}
    		}
     
     
    	}}

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