shufflefields.java

Java程序设计(美) David D. Riley著 机械工业出版社 书籍配套 代码

import javax.swing.*;
import java.awt.*;
public class ShuffleFields {
	private TextField topField, midField, bottomField;

	/**	post:	topField, midField and bottomField are instantiated 
	 *			and added to f 
	 */
	public ShuffleFields( JFrame f )   {
		Label directions;
		directions = new Label("Please type in the text fields.");
		directions.setBounds(50, 100, 500, 30);
		directions.setForeground(Color.blue);
		f.add(directions);
		topField = new TextField();
		topField.setBounds(250, 150, 100, 30);
		topField.repaint();
		f.add(topField, 0);
		midField = new TextField();
		midField.setBounds(250, 200, 100, 30);
		midField.repaint();
		f.add(midField, 0);
		bottomField = new TextField();
		bottomField.setBounds(250, 250, 100, 30);
		bottomField.repaint();
		f.add(bottomField, 0);
	}

	/** post:	topField.getText() == midField.getText()@pre
	 *			and  midField.getText() == bottomField.getText()@pre
	 *			and  bottomField.getText() == topField.getText()@pre 
	 */
	public void rotateUp()   {
		String topFieldAtPre = topField.getText();
		topField.setText( midField.getText() );
		midField.setText( bottomField.getText() );
		bottomField.setText( topFieldAtPre );
	}
	
	/** post:	topField.getText() == midField.getText()@pre
	 *			and  bottomField.getText() == midField.getText()@pre 
	 */
	public void copyMiddle()   {
		topField.setText( midField.getText() );
		bottomField.setText( midField.getText() );
	}
	
	/** post:	bottomField.getText() == midField.getText()@pre
	 *			and  midField.getText() == topField.getText()@pre
	 *			and  topField.getText() == bottomField.getText()@pre 
	 */
	public void rotateDown()   {
		String bottomFieldAtPre;
		bottomFieldAtPre = bottomField.getText();
		bottomField.setText( midField.getText() );
		midField.setText( topField.getText() );
		topField.setText( bottomFieldAtPre );
	}
}