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

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

Code :

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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);
	}
}
}

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

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.

Code :

---

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";
			}
		}
 
 
	}}

---