【计算机类职业资格】二级JAVA机试-37及答案解析.doc

1、二级 JAVA 机试-37 及答案解析(总分：100.00，做题时间：90 分钟)一、基本操作题(总题数：1，分数：30.00)1.本题利用递归方法求前 n 个自然数的和(n=10)。public class java1public static void main(Stringargs)int sum=add(10);System.out.println(“1+2+.+9+10=“+sum);public static int add(_)if(n=1)_;else_;（分数：30.00）_二、简单应用题(总题数：1，分数：40.00)2.本题中定义了一个简单的计算器，可以进行基本的四则运算

2、程序中包含 16 个按钮用来表示09、+、-、*、/、=运算符和小数点，程序顶部的文本框用来显示操作数以及结果。import java.awt.*;import java.awt.event.*;import javax.swing.*;public class java2public static void main(Stringargs)tryUIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName();catch(Exception e)JFrame frame=new CalculatorFrame();fram

3、e.show();class CalculatorPanel extends JPanel implements ActionListenerprivate JTextField display;private JButton btn;private double arg=0;private String op=“=“;private boolean start=true;public CalculatorPanel()setLayout(new BorderLayout();display=new JTextField(“0“);display.setEditable(false);add(

4、display,“North“);JPanel p=new JPanel();p.setLayout(new GridLayout(4,4);String buttons=“789/456*123-0.=+“;for(int i=0;ibuttons.length();i+)btn=new JButton(buttons.substring(i,i+1);p.add(btn);_;add(p,“Center“);public void actionPerformed(ActionEvent evt)String s=evt.getActionCommand();if(0=s.charAt(0)

5、else display.setText(display.getText()+s);start=false;elseif(start)if(s.equals(“-“)display.setText(s);start=false;else op=s;elsedouble x=_;calculate(x);op=s;start=true;public void calculate(double n)if(op.equals(“+“)arg+=n;else if(op.equals(“-“)arg-n;else if(op.equals(“*“)arg*=n;else if(op.equals(“/

6、)arg/=n;else if(op.equals(“=“)arg=n;display.setText(“+arg);class CalculatorFrame extends JFramepublic CalculatorFrame()setTitle(“java2“);setSize(220,180);addWindowListener(new WindowAdapter()public void windowClosing(WindowEvent e)System.exit(0););Container contentPane=getContentPane();contentPane.

7、add(new CalculatorPanel();（分数：40.00）_三、综合应用题(总题数：1，分数：30.00)3.本题的功能是用文本框来设定表盘中指针的位置。窗口中有一个画板和两个文本框，画板中绘制了一个表盘和时针、分针，通过文本框分别设定“时”和“分”，表盘中的时针和分针就会指到对应的位置上。import java.awt.*;import java.awt.event.*;import java.awt.geom.*;import javax.swing.*;import javax.swing.event.*;public class java3public static vo

8、id main(Stringargs)TextTestFrame frame=new TextTestFrame();frame.setDefauhCloseOperation(JFrame.EXIT_ON_CLOSE);frame.show();class TextTestFrame extends JFramepublic TextTestFrame()setTitle(“java3“);setSize(DEFAULT_WIDTH,DEFAULT_HEIGHT);Container contentPane=getContentPane();DocumentListener listener

9、new DocurnentListener();JPanel panel=new JPanel();hourField=new JTextField(“12“,3);panel.add(hourField);hourField.getDocument().addDocumentListener(this);minuteField=new JTextField(“00“,3);panel.add(minuteField);minuteField.getDocument().addDocumentListener(listener);contentPane.add(panel,BorderLay

10、out.SOUTH);clock=new ClockPanel();contentPane.add(clock,BorderLayout.CENTER);public void setClock()tryint hours=Integer.parseInt(hourField,getText().trim();int minutes=Integer.parseInt(minuteField.getText().trim();clock.setTime(hours,minutes);catch(NumberFormatException e)public static final int DEF

11、AULT_WIDTH=300;public static final int DEFAULT_HEIGHT=300;private JTextField hourField;private JTextField minuteField;private ClockPanel clock;private class clockFieldListener extends DocumentListenerpublic void insertUpdate(DocumentEvent e)setClock();public void removeUpdate(DocumentEvent e)setCloc

12、k();public void changedUpdate(DocumentEvent e)class ClockPanel extends JPanelpublic void paintComponent(Graphics g)super.paintComponent(g);Graphics2D g2=(Graphics2D)g;Ellipse2D circle=new Ellipse2D.Double(0,0,2*RADIUS,2*RADIUS);g2.draw(circle);double hourAngle=Math.toRadians(90-360*minutes/(12*60);d

13、rawHand(g2.hourAngle,HOUR_HAND_LENGTH);double minuteAngle=Math.toRadians(90-360*minutes/60);drawHand(g2,minuteAngle,MINUTE_HAND_LENGTH);public void drawHand(Graphics2D g2,double angle,double handLength)Point2D end=new Poim2D.Double(RADIUS+handLength*Math.cos(angle),RADIUS-handLength*Math.sin(angle);

14、Point2D center=new Point2D.Double(RADIUS,RADIUS);g2.draw(new Line2D.Double(center,end);public void setTime(int h,int m)minutesh*60+m：repaint();private double minutes=0;private double RADIUS=100;private double MINUTE_HAND_LENGTH=0.8*RADIUS;private double HOUR_HAND_LENGTH=0.6*RADIUS;（分数：30.00）_二级 JAVA

15、 机试-37 答案解析(总分：100.00，做题时间：90 分钟)一、基本操作题(总题数：1，分数：30.00)1.本题利用递归方法求前 n 个自然数的和(n=10)。public class java1public static void main(Stringargs)int sum=add(10);System.out.println(“1+2+.+9+10=“+sum);public static int add(_)if(n=1)_;else_;（分数：30.00）_正确答案：(第 1 处：int n第 2 处：return 1第 3 处：return n+add(n-1)解析：解析

16、 递归方法是一种调用程序本身并采用栈结构的算法，第 1 处定义参数类型；第 2 处是递归初值；第 3 处为递归运算。二、简单应用题(总题数：1，分数：40.00)2.本题中定义了一个简单的计算器，可以进行基本的四则运算。程序中包含 16 个按钮用来表示09、+、-、*、/、=运算符和小数点，程序顶部的文本框用来显示操作数以及结果。import java.awt.*;import java.awt.event.*;import javax.swing.*;public class java2public static void main(Stringargs)tryUIManager.setLo

17、okAndFeel(UIManager.getSystemLookAndFeelClassName();catch(Exception e)JFrame frame=new CalculatorFrame();frame.show();class CalculatorPanel extends JPanel implements ActionListenerprivate JTextField display;private JButton btn;private double arg=0;private String op=“=“;private boolean start=true;pub

18、lic CalculatorPanel()setLayout(new BorderLayout();display=new JTextField(“0“);display.setEditable(false);add(display,“North“);JPanel p=new JPanel();p.setLayout(new GridLayout(4,4);String buttons=“789/456*123-0.=+“;for(int i=0;ibuttons.length();i+)btn=new JButton(buttons.substring(i,i+1);p.add(btn);_

19、add(p,“Center“);public void actionPerformed(ActionEvent evt)String s=evt.getActionCommand();if(0=s.charAt(0)else display.setText(display.getText()+s);start=false;elseif(start)if(s.equals(“-“)display.setText(s);start=false;else op=s;elsedouble x=_;calculate(x);op=s;start=true;public void calculate(d

20、ouble n)if(op.equals(“+“)arg+=n;else if(op.equals(“-“)arg-n;else if(op.equals(“*“)arg*=n;else if(op.equals(“/“)arg/=n;else if(op.equals(“=“)arg=n;display.setText(“+arg);class CalculatorFrame extends JFramepublic CalculatorFrame()setTitle(“java2“);setSize(220,180);addWindowListener(new WindowAdapter(

21、)public void windowClosing(WindowEvent e)System.exit(0););Container contentPane=getContentPane();contentPane.add(new CalculatorPanel();（分数：40.00）_正确答案：(第 1 处：btn.addActionListener(this)第 2 处：Double.parseDouble(display.getText()解析：解析 第 1 处为按钮添加监听器；第 2 处获得输入数字并转化为 double 型。三、综合应用题(总题数：1，分数：30.00)3.本题的

22、功能是用文本框来设定表盘中指针的位置。窗口中有一个画板和两个文本框，画板中绘制了一个表盘和时针、分针，通过文本框分别设定“时”和“分”，表盘中的时针和分针就会指到对应的位置上。import java.awt.*;import java.awt.event.*;import java.awt.geom.*;import javax.swing.*;import javax.swing.event.*;public class java3public static void main(Stringargs)TextTestFrame frame=new TextTestFrame();frame.

23、setDefauhCloseOperation(JFrame.EXIT_ON_CLOSE);frame.show();class TextTestFrame extends JFramepublic TextTestFrame()setTitle(“java3“);setSize(DEFAULT_WIDTH,DEFAULT_HEIGHT);Container contentPane=getContentPane();DocumentListener listener=new DocurnentListener();JPanel panel=new JPanel();hourField=new

24、JTextField(“12“,3);panel.add(hourField);hourField.getDocument().addDocumentListener(this);minuteField=new JTextField(“00“,3);panel.add(minuteField);minuteField.getDocument().addDocumentListener(listener);contentPane.add(panel,BorderLayout.SOUTH);clock=new ClockPanel();contentPane.add(clock,BorderLay

25、out.CENTER);public void setClock()tryint hours=Integer.parseInt(hourField,getText().trim();int minutes=Integer.parseInt(minuteField.getText().trim();clock.setTime(hours,minutes);catch(NumberFormatException e)public static final int DEFAULT_WIDTH=300;public static final int DEFAULT_HEIGHT=300;private

26、 JTextField hourField;private JTextField minuteField;private ClockPanel clock;private class clockFieldListener extends DocumentListenerpublic void insertUpdate(DocumentEvent e)setClock();public void removeUpdate(DocumentEvent e)setClock();public void changedUpdate(DocumentEvent e)class ClockPanel ex

27、tends JPanelpublic void paintComponent(Graphics g)super.paintComponent(g);Graphics2D g2=(Graphics2D)g;Ellipse2D circle=new Ellipse2D.Double(0,0,2*RADIUS,2*RADIUS);g2.draw(circle);double hourAngle=Math.toRadians(90-360*minutes/(12*60);drawHand(g2.hourAngle,HOUR_HAND_LENGTH);double minuteAngle=Math.to

28、Radians(90-360*minutes/60);drawHand(g2,minuteAngle,MINUTE_HAND_LENGTH);public void drawHand(Graphics2D g2,double angle,double handLength)Point2D end=new Poim2D.Double(RADIUS+handLength*Math.cos(angle),RADIUS-handLength*Math.sin(angle);Point2D center=new Point2D.Double(RADIUS,RADIUS);g2.draw(new Line

29、2D.Double(center,end);public void setTime(int h,int m)minutesh*60+m：repaint();private double minutes=0;private double RADIUS=100;private double MINUTE_HAND_LENGTH=0.8*RADIUS;private double HOUR_HAND_LENGTH=0.6*RADIUS;（分数：30.00）_正确答案：(第 1 处：DocumentListener listener=new ClockFieldListener()第 2 处：hourField.getDocument().addDocumentListener(listener)第 3 处：private class ClockFieldListener implements DocumentListener)解析：解析 第 1 处从后面程序可以看出 ClockFieldListener 类扩展了 DocumentListener，此处应使用继承后的子类；第 2 处注册窗体的监听器，参数应为事件源。第 3 处实现的是接口，应使用implements。