2020/10/24 Java学习记录No.6

Posted 2020-12-20 cyades

 

 

 1.他们是Throwable的两个平行类。Expection是所有异常类的祖先，而Error是错误类的祖先。

　　①Error不是程序需要捕获和处理的，发生时程序将会停止。

　　②Exception有许多子类，都是按照包的形式组织的，程序需要应对这些异常对象进行相应的处理。

2.

 

 

 

//隐式声明抛出
1 import java.util.*;
2 class TestEmptyStack {
3     public static void main(String[] args){
4            Stack st = new Stack();
5            Object ob = st.pop();  
6     }
7 }

//显示声明抛出
import java.io.*;
class TestScreenIn{
   public static void main(String[] args) throw IOException{
     BufferedReader keyin = new BufferedReader(new 
        InputStreamReader(System.in));
    String c1;
    int i=0;
    String[] e = new String[10];        
    while(i<10){
        c1 = keyin.readLine();
        e[i] = c1;              
        i++;
    }                
   }

}

 

 3.

package com.company;

import java.util.EmptyStackException;
import java.util.Stack;

class A{
    int v = 1;
    public int getV() {
        return v;
    }
}

public class test {
    public static void Arithmetic() {
        int a = 1, b = 0;
        try{
            int c = a / b;
        } catch (ArithmeticException ae) {
            System.out.println(ae.getClass().getName()+" has been throw");
        } finally {
            System.out.println("ArithmeticException is over!
");
        }
    }

    public static void NullPointer() {

        try {
            A a = null;
            a.getV();
        } catch (NullPointerException npe) {
            System.out.println(npe.getClass().getName()+" has been throw");
        } finally {
            System.out.println("NullPointerException is over！
");
        }
    }

    public static void EmptyStack() {
        Stack s = new Stack();

        try{
            s.pop();
            System.out.println("Pop");
        } catch (EmptyStackException ese) {
            System.out.println(ese.getClass().getName()+" has been throw");
        } finally {
            System.out.println("EmptyStackException is over！
");
        }
    }

    public static void IndexOutOfBounds() {
        int[] a = new int[3];
        for (int i = 0; i<3 ; i++ ) {
            a[i] = i;
        }
        try{
            System.out.println(a[4]);
        } catch (IndexOutOfBoundsException ioe) {
            System.out.println(ioe.getClass().getName()+" has been throw");
        } finally {
            System.out.println("IndexOutOfBoundsException is over！
");
        }
    }

    public static void NegativeArraySize() {
        try{
            int[] a = new int[-3];
        } catch (NegativeArraySizeException nase) {
            System.out.println(nase.getClass().getName()+" has been throw");
        } finally {
            System.out.println("NegativeArraySizeException is over！
");
        }
    }

    public static void main(String[] args) {
        test.Arithmetic();
        test.EmptyStack();
        test.IndexOutOfBounds();
        test.NegativeArraySize();
        test.NullPointer();
    }

}

 

 

4.

 

 

 

import java.util.*;

public class myexception extends Exception{
    myexception(String msg){
        super(msg);
    }
    static void throwOne(String c) throws myexception{
        //String a = "cya";
        if(c.equals("cya")){
            throw new myexception("you cant say that");
        }
    }
    public  static void main(String[] args){
        Scanner in = new Scanner(System.in);
        String s = in.nextLine();
        try {
            myexception.throwOne(s);
        }catch (myexception b){
            b.printStackTrace();
        }
    }
}