【软件测试】闰年问题（不考虑非法输入）

import javax.swing.JOptionPane;

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;


public class task extends Application {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        task.launch( args );
    }
    
    private TextField textfield = new TextField();
    
    @Override
    public void start(Stage arg0) throws Exception {
        // TODO Auto-generated method stub
        arg0.setTitle( "Testing" );
        
        HBox hbox = new HBox( 8 );
        textfield.setPrefColumnCount( 25 );
        hbox.setAlignment( Pos.CENTER_LEFT );
        Button btn = new Button();
        btn.setText( "提交" );
        btn.setOnAction( new Listener() );
        hbox.getChildren().addAll( new Label( "  请输入年份: "), textfield, btn );
        
        arg0.setScene( new Scene( hbox, 460, 50 ));
        arg0.show();
    }
    
    public class Listener implements EventHandler<ActionEvent> {

        @Override
        public void handle(ActionEvent arg0) {
            // TODO Auto-generated method stub
            String str = textfield.getText();
            String inf = "";
            if( isLeap( Integer.parseInt( str ) ) ) {
                inf = "输入年份为闰年";
            }
            else {
                inf = "输入年份非闰年";
            }
            
            JOptionPane.showMessageDialog( null, inf, "information", 
                    JOptionPane.INFORMATION_MESSAGE );
        }
    }
    
    private boolean isLeap( int year ) {
        if( year % 4 != 0 ) {
            return false;
        }
        else if( year % 100 != 0 ) {
            return true;
        }
        else if( year % 400 != 0 ) {
            return false;
        }
        else {
            return true;
        }
    }
}