简明现代魔法 -> Java编程语言 -> SWT之路：递归计算阶乘

SWT之路：递归计算阶乘

2009-11-30

递归是一个强大的算法，一个简单的例子就是使用递归来计算某数的阶乘。

本程序实现，输入任意一个整数，返回它的阶乘。

package SWT;

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.SelectionAdapter;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Group;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Text;

public class factorial {

	protected Shell shell;
	private Text text;
	static Label resultShow;

	/**
	 * Launch the application.
	 * @param args
	 */
	public static void main(String[] args) {
		try {
			factorial window = new factorial();
			window.open();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	/**
	 * Open the window.
	 */
	public void open() {
		Display display = Display.getDefault();
		createContents();
		shell.open();
		shell.layout();
		while (!shell.isDisposed()) {
			if (!display.readAndDispatch()) {
				display.sleep();
			}
		}
	}

	/**
	 * Create contents of the window.
	 */
	protected void createContents() {
		shell = new Shell();
		shell.setSize(450, 300);
		shell.setText("阶乘计算");
		{
			Group group = new Group(shell, SWT.NONE);
			group.setText("输入需要计算阶乘的数");
			group.setBounds(10, 10, 422, 120);
			{
				text = new Text(group, SWT.BORDER);
				text.setBounds(170, 39, 70, 18);
			}
			{
				Button button = new Button(group, SWT.NONE);
				button.setBounds(170, 77, 72, 22);
				button.setText("计算");
				button.addSelectionListener(new SelectionAdapter() {      
                    public void widgetSelected(SelectionEvent e) {      
                        // 读取输入      
                        int input = Integer.parseInt(text.getText());  
                        int result = fac(input);
                        resultShow.setText(input + "的阶乘为" + result);
                           
                    }      
                });     
			}
		}
		{
			Group group = new Group(shell, SWT.NONE);
			group.setText("结果");
			group.setBounds(10, 141, 422, 115);
			{
				resultShow = new Label(group, SWT.NONE);
				resultShow.setAlignment(SWT.CENTER);
				resultShow.setBounds(50, 39, 328, 66);
				//label.setText("New Label");
			}
		}

	}
	
	public int fac(int num){
		if(num == 1){
			return 1;
		}
		return num * fac(num-1);
	}
}