Java期末题库 – 小飞侠

根据如下图所示数据库信息，完成1-3小题。

（1）使用JDBC数据库连接技术，编写JDBCUtil工具类，在该类中定义getCon方法用于获得与数据库的连接对象，定义closeAll方法用于释放连接对象等资源。

import java.sql.*;

public class JDBCUtil {
    private static String user="用户名";
    private static String password="密码";
    private static String url="jdbc:mysql://localhost:3306/数据库名";
    private static String driver="com.mysql.jdbc.Driver";
    /**
     * 连接数据库, 返回 Connection
     */
    public static Connection getCon() {
        try {
            return DriverManager.getConnection(url, user, password);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * 关闭连接
     */
    public static void closeAll(ResultSet set, PreparedStatement statement, Connection connection) {
        try {
            if (set != null) {
                set.close();
            }
            if (statement != null) {
                statement.close();
            }
            if (connection != null) {
                connection.close();
            }
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }
    }
}

（2）应用类的封装性，创建book表对应的类，其中book表存储图书id（主键、自增）、书名、价格、作者、库存量等信息。

public class Book {
    private Integer id;
    private String name;
    private Double price;
    private String author;
    private Integer reserve;

    public Book() {
    }

    public Book(Integer id, String name, Double price, String author, Integer reserve) {
        this.id = id;
        this.name = name;
        this.price = price;
        this.author = author;
        this.reserve = reserve;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Double getPrice() {
        return price;
    }

    public void setPrice(Double price) {
        this.price = price;
    }

    public String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public Integer getReserve() {
        return reserve;
    }

    public void setReserve(Integer reserve) {
        this.reserve = reserve;
    }

    @Override
    public String toString() {
        return "Book{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", price=" + price +
                ", author='" + author + '\'' +
                ", reserve=" + reserve +
                '}';
    }
}

（3）创建BookDao类，完成增加图书信息的方法，并编写Test测试类测试。

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class BookDao {
    static Connection con = null;
    static ResultSet set=null;
    static PreparedStatement ps=null;

    public static void addBook(String name,double price,String author,int reserve) {
        String sql="insert into book values(null,?,?,?,?);";
        try {
            con=JDBCUtil.getCon();
            ps=con.prepareStatement(sql);
            ps.setString(1,name);
            ps.setDouble(2,price);
            ps.setString(3,author);
            ps.setInt(4,reserve);
            ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            JDBCUtil.closeAll(null,ps,con);
        }
    }

    public static void select(){
        String sql="select *from book";
        con=JDBCUtil.getCon();
        try {
            ps=con.prepareStatement(sql);
            set= ps.executeQuery();
            while (set.next()){
                System.out.println("Book{" +
                        "id=" + set.getInt("id") +
                        ", name='" + set.getString("name") + '\'' +
                        ", price=" + set.getDouble("price") +
                        ", author='" + set.getString("author") + '\'' +
                        ", reserve=" + set.getInt("reserve") +
                        '}');
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            JDBCUtil.closeAll(set,ps,con);
        }
    }
}

Test

public class Test {
    public static void main(String[] args) {
        BookDao.addBook("老人与海",32.1,"海明威",4);
        BookDao.select();
    }
}

2、使用循环和break、continue等流程控制语句，计算1-n全部偶数的和，n的值在控制台输入。

import java.util.Scanner;

/**
 * @author whlie(true){learn}
 */
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int sum = 0;
        for (int index = 1; index < n; index++) {
            if (index % 2 != 0) {
                continue;
            }
            sum += index;
        }
        System.out.println(sum);
    }
}

3、一张纸的厚度大约是0.08mm，对折多少次之后能达到或超过珠穆朗玛峰的高度（8848.13米）。

public class Main {
    public static void main(String[] args) {
        //为了便于计算将原值扩大100倍
        long start=8;
        //1mm=0.001m
        long end=884813000;
        long count=0;
        while (start<end){
            start*=2;
            count++;
        }
        System.out.println(count);
    }
}

4、创建一个存储13张牌面值的集合，如“A,1,2…Q,K”,采用高级for循环或者迭代器方法遍历集合数据输出。

import java.util.*;

/**
 * @author whlie(true){learn}
 */
public class Main {
    public static void main(String[] args) {
        String[] card=new String[]{"2","3","4","5","6","7","8","9","10","J","Q","K","A"};
        List<String> list = Arrays.asList(card);
        //高级for循环
        for(String s:list){
            System.out.print(s+" ");
        }
        //迭代器
        Iterator<String> iterator = list.iterator();
        while (iterator.hasNext()){
            System.out.print(iterator.next()+" ");
        }
    }
}

5、计算控制台输入的任意字符串中每个字符出现的次数。如abbbcccdabc，输出如：

a出现次数为:2

b出现次数为:4

c出现次数为:4

d出现次数为:1

这道题的题意不明，控制台输入字符串的范围没给，从样例推测字符串只包含小写字符。

import java.util.*;

/**
 * @author whlie(true){learn}
 */
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String s= scanner.nextLine();
        char[] chars = s.toCharArray();
        int[] array=new int[26];
        for(char c:chars){
            array[c-'a']++;
        }
        for (int i = 0; i < array.length; i++) {
            if (array[i]>0){
                System.out.println((char)(i+'a')+"出现次数为:"+array[i]);
            }
        }
    }
}

6、一辆卡车违反交通规则，撞人后逃跑。现场有三人目击事件，但都没有记住车号，只记下车号的一些特征。

甲说：牌照的前两位数字是相同的；

乙说：牌照的后两位数字是相同的，但与前两位不同；

丙是数学家，他说：四位的车号刚好是一个整数的平方。请根据以上线索求出车号。

public class Main {
    public static void main(String[] args) {
        for (int i = 1000; i < 10000; i++) {
            if (judgeSame(i)&&judgeSqrt(i)){
                System.out.println(i);
            }
        }
    }

    /**
     * 判断甲和乙的条件
     * 1.前两位相同
     * 2.后两位相同
     * 3.前两位和后两位不能相同
     */
    public static boolean judgeSame(int i){
        char[] chars = (i + "").toCharArray();
        return chars[0]==chars[1]&&chars[2]==chars[3]&&chars[0]!=chars[3];
    }

    /**
     * 判断丙的条件
     * 1.是否为完全平方数
     */
    public static boolean judgeSqrt(int i){
        double a=Math.sqrt(i);
        return a==(int)a;
    }
}

7、马克思手稿中有一道趣味数学问题：有30个人，其中有男人、女人和小孩，在一家饭馆吃饭花了50先令；每个男人花3先令，每个女人花2先令，每个小孩花1先令；问男人、女人和小孩各有几人？

public class Main {
    public static void main(String[] args) {
        int count=1;
        for (int i = 1; i < 16; i++) {
            for (int j = 1; j < 25; j++) {
                for (int k = 1; k < 50; k++) {
                    if (i+j+k==30&&3*i+2*j+1*k==50){
                        System.out.println("第"+(count++)+"种可能:");
                        System.out.print("男人:"+i+"个 " +
                                         "女人:"+j+"个 " +
                                         "小孩:"+k+"个\n");
                    }
                }
            }
        }
    }
}

8、中国有句俗语叫“三天打鱼两天晒网”。某人从1990年1月1日起开始“三天打鱼两天晒网”，问这个人在以后的某一天中是“打鱼”还是“晒网”？

个人理解:三天打鱼两天晒网是指先连续打三天鱼再连续晒两天网，5天一次循环

1,2,3天打鱼，4,5天晒网，第0天相当于上次循环的第5天

import java.time.LocalDate;
import java.time.temporal.ChronoUnit;
import java.util.*;

/**
 * @author whlie(true){learn}
 */
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请依次输入年月日,以空格间隔:");
        int year=scanner.nextInt();
        int month=scanner.nextInt();
        int day = scanner.nextInt();
        long between = ChronoUnit.DAYS.between(LocalDate.of(1990, 1, 1),
                                               LocalDate.of(year, month, day));
        long result=(between+1)%5;
        System.out.println(result<4?result==0?"晒网":"打鱼":"晒网");
    }
}

9、创建一个名为Shape的接口，接口内有一个计算面积的抽象方法。定义一个Circle类，实现Shape接口，并实现接口里的抽象方法。

public interface Shape {
    public double area(double r);
}

public class Circle implements Shape{
    @Override
    public double area(double r) {
        return r*r*Math.PI;
    }
}

10、创建如图所示的窗口。

import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;


public class TextMain {
    public static String Signin;
    public static String register;
    JFrame jFrame;
	public static void main(String[] args) {
		init();
	}
	public static void init()
	{
		
		JFrame jFrame=new JFrame("hello");
		jFrame.setBounds(200, 200, 500, 400);
		jFrame.setLayout(null);
		
		JLabel jLabel1=new JLabel();
		jLabel1.setBounds(130, 100, 100, 100);
		jLabel1.setText("姓名:");
		jFrame.add(jLabel1);
		
		JLabel jLabel2=new JLabel();
		jLabel2.setBounds(130, 150, 100, 100);
		jLabel2.setText("密码:");
		jFrame.add(jLabel2);
		
		final JTextField jTextField=new JTextField();
		jTextField.setBounds(165, 135, 200, 30);
		jFrame.add(jTextField);
		
		
		final JTextField jTextField1=new JTextField();
		jTextField1.setBounds(165, 185, 200, 30);		
		jFrame.add(jTextField1);
		
		
		JButton jButton=new JButton();
		jButton.setBounds(130, 250, 85, 50);
		jButton.setText("登录");
		jFrame.add(jButton);
		
		JButton jButton1=new JButton();
		jButton1.setBounds(280, 250, 85, 50);
		jButton1.setText("注册");
		jFrame.add(jButton1);
		jFrame.setVisible(true);
	}
}

11、给上述窗口的登录按钮绑定点击事件，点击后获取用户在文本框输入的姓名和密码，打印输出到控制台上。(在10的基础上增加键盘监听事件)

    jTextField.addKeyListener(new KeyListener() {
			
			@Override
			public void keyTyped(KeyEvent e) {
				// TODO 自动生成的方法存根
				if(e.getKeyChar()==KeyEvent.VK_ENTER&&!jTextField.getText().equals(""))
				{
					Signin=jTextField.getText();
					System.out.println("姓名为:"+Signin);
				}
			}
			
			@Override
			public void keyReleased(KeyEvent e) {}
			
			@Override
			public void keyPressed(KeyEvent e) {}
		});
		
      jTextField1.addKeyListener(new KeyListener() {
			
			@Override
			public void keyTyped(KeyEvent e) {
				if(e.getKeyChar()==KeyEvent.VK_ENTER&&!jTextField1.getText().equals(""))
				{
					register=jTextField1.getText();
					System.out.println("密码为:"+register);
				}
			}
			
			@Override
			public void keyReleased(KeyEvent e) {}
			
			@Override
			public void keyPressed(KeyEvent e) {}
		});
        
      jButton.addActionListener(new ActionListener() {
		
		@Override
		public void actionPerformed(ActionEvent e) {
			Signin=jTextField.getText();
			System.out.println("姓名为:"+Signin);
			register=jTextField1.getText();
			System.out.println("密码为:"+register);
		}
	});

12、使用Canvas类，绘制红色字符串“hello”，显示在JFrame窗口中。

import java.awt.Canvas;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import javax.swing.JFrame;


public class TextMain {
    public static String Signin;
    public static String register;
    JFrame jFrame;
	public static void main(String[] args) {
		JFrame jFrame1=new JFrame("Canvas");
		jFrame1.setBounds(200, 200, 500, 400);
		jFrame1.setLayout(null);
		
		Can can=new Can();
		can.setBounds(20, 20, 400, 400);
		jFrame1.add(can);
		
		jFrame1.setVisible(true);
	}
}
class Can extends Canvas{
	@Override
	public void paint(Graphics g) {
		super.paint(g);
		g.setFont(new Font("黑体", Font.BOLD, 50));
		g.setColor(new Color(255,0,0));
		g.drawString("hello", 100, 100);
	}
}

原文链接：https://blog.csdn.net/m0_55997161/article/details/125109609

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