Lösung Übung 17: Beispiel für Exception-Handling

import java.awt.*;
import java.awt.event.*;
import java.applet.*;

public class DivisionsApp extends Applet {

	Label prompt1, prompt2;
	TextField input1, input2;
	double result;
	
	public void init() {
		prompt1 = new Label("Geben Sie eine Zahl ein:");
		input1 = new TextField( 10 );
		prompt2 = new Label("Geben Sie eine Teiler ein " +
					"drücken Sie Enter:");
		input2 = new TextField( 10 );		
		input2.addActionListener( new FieldActionListener() );
		add( prompt1 );
		add( input1 );
		add( prompt2 );
		add( input2 );
	}

	class FieldActionListener implements ActionListener {
		public void actionPerformed( ActionEvent e ) {
			int number1, number2;
			try {
				number1 = Integer.parseInt( input1.getText() );

				number2 = Integer.parseInt( input2.getText() );

			}
			catch( NumberFormatException exception ) {
				showStatus( exception.toString() );
				return;		
			}
			finally {
				input1.setText("");
				input2.setText("");
				Toolkit.getDefaultToolkit().beep();
			}
			
			
			try {
				double result = quotient( number1, number2 );
		
				showStatus( number1 + " / " + number2 + " = " +
						Double.toString( result ) );			
			}
			catch( DivideByZeroException exception ) {
				showStatus( exception.toString() );
			}
		}
	}

	public double quotient( int numerator, int denominator ) 
			throws DivideByZeroException {

		if( denominator == 0 )
			throw new DivideByZeroException();
			
		return( (double)numerator/(double)denominator );	
	}
}

class DivideByZeroException extends Exception {

	public DivideByZeroException() {
		super("Versuch durch Null zu teilen gescheitert");
	}	
}

																						    		
															
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