eclipse异常类之自定义异常和assert

public class MyException extends Exception{
		public MyException() {
			super();	
		}
		public MyException(String massage ) {
			super(massage);
		}
}

public class UserService {

	public User login(String username,String password)throws MyException {
		if(!"abcd".equals(username)) {
			throw new MyException("用户名错误");
		}
		if(!"1234".equals(password)) {
			throw new MyException("密码错误");
		}
		User user=new User("abcd","1234",18,"男");
		return user;
	}
}

public class User {
	private String username;
	private String password;
	private int age;
	private String sex;
	
	public User() {
		super();
	}
	public User(String username, String password, int age, String sex) {
		super();
		this.username = username;
		this.password = password;
		this.age = age;
		this.sex = sex;
	}
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public String getPassword() {
		return password;
	}
	public void setPassword(String password) {
		this.password = password;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	public String getSex() {
		return sex;
	}
	public void setSex(String sex) {
		this.sex = sex;
	}
    @Override
	public String toString() {
		return "User [username=" + username + ", password=" + password + ", age=" + age + ", sex=" + sex + "]";
	}
}

import java.util.Scanner;

public class LoginDemo {

	public static void main(String[] args) {
			
		Scanner input=new Scanner(System.in);
		System.out.println("请输入用户名");
		String name=input.nextLine();
		System.out.println("请输入密码");
		String pass=input.nextLine();
		
		UserService us=new UserService();
		try {
		User user=us.login(name, pass);
		System.out.println("登录成功");
		System.out.println(user);
	}catch(MyException e) {
		e.printStackTrace();
		}
	}

}

Exception:在编译期检查，在调用抛出这个异常的方法时，必须使用try、、、catch

RuntimeException：在运行期检查，在调用抛出这个异常的方法时，不可以使用try、、、catch

在使用自定义异常时，根据实际的业务需求，来决定使用哪一个作为父类

public class MyException extends RuntimeException{
		public MyException() {
			super();	
		}
		public MyException(String massage ) {
			super(massage);
		}
}
~~~~~~~~~~~~~~~~~~~~~~~~


import java.util.Scanner;

public class LoginDemo {

	public static void main(String[] args) {
			
		Scanner input=new Scanner(System.in);
		System.out.println("请输入用户名");
		String name=input.nextLine();
		System.out.println("请输入密码");
		String pass=input.nextLine();
		
		UserService us=new UserService();
		
		User user=us.login(name, pass);
		System.out.println("登录成功");
		System.out.println(user);
	
	}

}

assert关键字，表示断言

    当程序执行到某个位置的时候，程序中的某个变量的取值肯定是预期的结果，那么这种操作可以使用断言完成

assert的表达式：

public class AsserDemo {

	public static void main(String[] args) {
		
		int result =add(10,8);
		assert result==10:"结果不正确";
		
	}

	
	private static int add(int a,int b) {
		return a+b;
	}
}

这样直接运行没有结果

运行程序是需要添加JVM参数-ea,断言才能起效果