1.定义一个图形接口，一个有抽象方法。求周长子类实现接口，创建子类对象求周长

interface Shape{
	double girth(int length);
}
class Circle implements Shape{
	int r;
	public Circle(int r) {
		super();
		this.r = r;
	}
	@Override
	public double girth(int length) {
		// TODO Auto-generated method stub
		return 2*3.14*length;
	}
}
public class ShapeTest {

	public static void main(String[] args) {
		Circle c = new Circle(1);
		System.out.println(c.girth(c.r));
	}
}

2.随机输出500-560之间的30个，存到数组中，并升序排序

public class RandomTest {
	public static void main(String[] args) {
		int[] array = new int[30];
		Random random = new Random();
		for(int i = 0;i<array.length;i++) {
			array[i] = random.nextInt(61)+500;
		}
		System.out.println("未排序");
		for(int arr:array) {
			System.out.print(arr+"\t");
		}
		Arrays.sort(array);
		System.out.println("\r\n排序");
		for(int arr:array) {
			System.out.print(arr+"\t");
		}
	}
}

3.输出流输出Stu对象，序列化，输入流读取到控制台

public class ObjectTest {
	public static void main(String[] args) throws FileNotFoundException, IOException, ClassNotFoundException {
		Stu s1 = new Stu("1","a");
		Stu s2 = new Stu("2","b");
		Stu s3 = new Stu("1","a");
		HashSet hs = new HashSet();
		hs.add(s1);
		hs.add(s2);
		hs.add(s3);
		ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("D:\\object.txt"));
		Iterator iterator = hs.iterator();
		while(iterator.hasNext()) {
			Stu s = (Stu)iterator.next();
			oos.writeObject(s);
		}
		oos.close();
		ObjectInputStream ois = new ObjectInputStream(new FileInputStream("D:\\object.txt"));
		Stu stu1 = (Stu)ois.readObject();
		Stu stu2 = (Stu)ois.readObject();
		System.out.println(stu1);
		System.out.println(stu2);
		ois.close();
	}
}

class Stu implements Serializable{
	String id,name;
	public Stu() {
		super();
		// TODO Auto-generated constructor stub
	}
	public Stu(String id, String name) {
		super();
		this.id = id;
		this.name = name;
	}
	@Override
	public String toString() {
		return "id=" + id + ", name=" + name ;
	}
	@Override
	public int hashCode() {
		// TODO Auto-generated method stub
		return this.id.hashCode();
	}
	@Override
	public boolean equals(Object obj) {
		Stu s = (Stu)obj;
		return this.id.equals(s.id);
	}
	
}

4.点击按钮出现弹窗

public class JframeTest {

	public static void main(String[] args) {
		JFrame jf = new JFrame("标题");
		jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		jf.setBounds(500, 200,400, 300);
		//窗体上放中间容器
		JPanel pan = new JPanel();
		//面板上摆放组件 
		JLabel label1 = new JLabel("账号");
		JTextField text = new JTextField(10);
//		label1.setBounds(100, 10, 80, 70);
		JLabel label2 = new JLabel("密码");
//		label2.setBounds(100, 10, 80,90);
		JButton button = new JButton("点击");
		
		//将组件添加到面板上
		
		pan.add(label1);
		pan.add(text);
		pan.add(label2);
		pan.add(button);
		button.addActionListener(new ActionListener() {
			@Override
			public void actionPerformed(ActionEvent e) {
				JOptionPane.showMessageDialog(jf, "这是消息框");
			}
		});
		//将面板添加到窗体上
		jf.add(pan);
		//显示窗体
		jf.setVisible(true);
	}

}

5.在窗体上有标签，文本框，按钮，在文本框输入账号，点击确定，在数据库中查找是否存在

public class SelectTest {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		JFrame jf = new JFrame("查询");
		jf.setBounds(500, 200, 400 ,300);
		jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		//窗体上放中间容器
		JPanel jp = new JPanel();
		//面板上摆放组件
		JLabel jl = new JLabel("请输入账号");
		JTextField field = new JTextField(15);
		JButton btn = new JButton("查找");
		//将组件添加到面板上
		jp.add(jl);
		jp.add(field);
		jp.add(btn);
		//将面板添加到窗体上
		jf.add(jp);
		jf.setVisible(true);
		//事件处理
		btn.addActionListener(new ActionListener() {
			
			@Override
			public void actionPerformed(ActionEvent e) {
				Connection con = null;
				Statement sta = null;
				ResultSet rs = null;
				String url = "jdbc:mysql://localhost:3306/teacherinfo?serverTimezone=UTC&useSSL=false";
				String user = "root";
				String password = "123456";
				
				try {
					Class.forName("com.mysql.cj.jdbc.Driver");
					con = DriverManager.getConnection(url, user, password);
					sta = con.createStatement();
					rs = sta.executeQuery("select * from info");
					boolean flag = false;
					while(rs.next()) {
						int id = rs.getInt(1);
						String idTxt = field.getText();
						if (idTxt.equals(String.valueOf(id))) {
							flag = true;
							break;
						}
						
					}
					if (flag==true) {
						JOptionPane.showMessageDialog(jf, "查找到了");
					}else {
						JOptionPane.showMessageDialog(jf, "没有找到");
					}
				} catch (ClassNotFoundException e1) {
					// TODO Auto-generated catch block
					e1.printStackTrace();
				} catch (SQLException e1) {
					// TODO Auto-generated catch block
					e1.printStackTrace();
				}finally {
					if (rs!=null) {
						try {
							rs.close();
						} catch (SQLException e1) {
							// TODO Auto-generated catch block
							e1.printStackTrace();
						}
						
					}
					if (sta!=null) {
						try {
							sta.close();
						} catch (SQLException e1) {
							// TODO Auto-generated catch block
							e1.printStackTrace();
						}
					}
					if(con!=null) {
						try {
							con.close();
						} catch (SQLException e1) {
							// TODO Auto-generated catch block
							e1.printStackTrace();
						}
					}
				}
				
			}
		});
	}

}