package com.example;
import java. util .Scanner ;
public class AllDemo
{
   public static void main (String [] args )
   {
      System . out. println( "----歡迎使用命令行除法計(jì)算器----" ) ;
      CMDCalculate ();
   }
   public static void CMDCalculate ()
   {
      Scanner scan = new Scanner ( System. in );
      int num1 = scan .nextInt () ;
      int num2 = scan .nextInt () ;
      int result = devide (num1 , num2 ) ;
      System . out. println( "result:" + result) ;
      scan .close () ;
   }
   public static int devide (int num1, int num2 ){
      return num1 / num2 ;
   }
}
/*****************************************
----歡迎使用命令行除法計(jì)算器----
0
Exception in thread "main" java.lang.ArithmeticException : / by zero
   at com.example.AllDemo.devide( AllDemo.java:30 )
   at com.example.AllDemo.CMDCalculate( AllDemo.java:22 )
   at com.example.AllDemo.main( AllDemo.java:12 )
----歡迎使用命令行除法計(jì)算器----
r
Exception in thread "main" java.util.InputMismatchException
   at java.util.Scanner.throwFor( Scanner.java:864 )
   at java.util.Scanner.next( Scanner.java:1485 )
   at java.util.Scanner.nextInt( Scanner.java:2117 )
   at java.util.Scanner.nextInt( Scanner.java:2076 )
   at com.example.AllDemo.CMDCalculate( AllDemo.java:20 )
   at com.example.AllDemo.main( AllDemo.java:12 )
*****************************************/

@Test
public void testException() throws IOException
{
  //FileInputStream的構(gòu)造函數(shù)會(huì)拋出FileNotFoundException
  FileInputStream fileIn = new FileInputStream("E:\\a.txt");
  int word;
  //read方法會(huì)拋出IOException
  while((word = fileIn.read())!=-1)
  {
    System.out.print((char)word);
  }
  //close方法會(huì)拋出IOException
  fileIn.clos
}

try{
   //try塊中放可能發(fā)生異常的代碼。
   //如果執(zhí)行完try且不發(fā)生異常，則接著去執(zhí)行finally塊和finally后面的代碼（如果有的話）。
   //如果發(fā)生異常，則嘗試去匹配catch塊。
}catch(SQLException SQLexception){
  //每一個(gè)catch塊用于捕獲并處理一個(gè)特定的異常，或者這異常類型的子類。Java7中可以將多個(gè)異常聲明在一個(gè)catch中。
  //catch后面的括號(hào)定義了異常類型和異常參數(shù)。如果異常與之匹配且是最先匹配到的，則虛擬機(jī)將使用這個(gè)catch塊來處理異常。
  //在catch塊中可以使用這個(gè)塊的異常參數(shù)來獲取異常的相關(guān)信息。異常參數(shù)是這個(gè)catch塊中的局部變量，其它塊不能訪問。
  //如果當(dāng)前try塊中發(fā)生的異常在后續(xù)的所有catch中都沒捕獲到，則先去執(zhí)行finally，然后到這個(gè)函數(shù)的外部caller中去匹配異常處理器。
  //如果try中沒有發(fā)生異常，則所有的catch塊將被忽略。
}catch(Exception exception){
  //...
}finally{
  //finally塊通常是可選的。
  //無論異常是否發(fā)生，異常是否匹配被處理，finally都會(huì)執(zhí)行。
  //一個(gè)try至少要有一個(gè)catch塊，否則， 至少要有1個(gè)finally塊。但是finally不是用來處理異常的，finally不會(huì)捕獲異常。
 //finally主要做一些清理工作，如流的關(guān)閉，數(shù)據(jù)庫連接的關(guān)閉等。
}

public static void main(String[] args){
    try {
      foo();
    }catch(ArithmeticException ae) {
      System.out.println("處理異常");
    }
}
public static void foo(){
    int a = 5/0; //異常拋出點(diǎn)
    System.out.println("為什么還不給我漲工資!!!"); //////////////////////不會(huì)執(zhí)行
}

public void foo() throws ExceptionType1 , ExceptionType2 ,ExceptionTypeN
{
   //foo內(nèi)部可以拋出 ExceptionType1 , ExceptionType2 ,ExceptionTypeN 類的異常，或者他們的子類的異常對(duì)象。
}

public void save(User user)
{
   if(user == null)
     throw new IllegalArgumentException("User對(duì)象為空");
   //......
}

public class Throwable implements Serializable {
  private Throwable cause = this;
  public Throwable(String message, Throwable cause) {
    fillInStackTrace();
    detailMessage = message;
    this.cause = cause;
  }
   public Throwable(Throwable cause) {
    fillInStackTrace();
    detailMessage = (cause==null ? null : cause.toString());
    this.cause = cause;
  }
  //........
}

public static void main(String[] args)
{
  System.out.println("請(qǐng)輸入2個(gè)加數(shù)");
  int result;
  try
  {
    result = add();
    System.out.println("結(jié)果:"+result);
  } catch (Exception e){
    e.printStackTrace();
  }
}
//獲取輸入的2個(gè)整數(shù)返回
private static List<Integer> getInputNumbers()
{
  List<Integer> nums = new ArrayList<>();
  Scanner scan = new Scanner(System.in);
  try {
    int num1 = scan.nextInt();
    int num2 = scan.nextInt();
    nums.add(new Integer(num1));
    nums.add(new Integer(num2));
  }catch(InputMismatchException immExp){
    throw immExp;
  }finally {
    scan.close();
  }
  return nums;
}
//執(zhí)行加法計(jì)算
private static int add() throws Exception
{
  int result;
  try {
    List<Integer> nums =getInputNumbers();
    result = nums.get(0) + nums.get(1);
  }catch(InputMismatchException immExp){
    throw new Exception("計(jì)算失敗",immExp); /////////////////////////////鏈化:以一個(gè)異常對(duì)象為參數(shù)構(gòu)造新的異常對(duì)象。
  }
  return result;
}
/*
請(qǐng)輸入2個(gè)加數(shù)
r 1
java.lang.Exception: 計(jì)算失敗
  at practise.ExceptionTest.add(ExceptionTest.java:53)
  at practise.ExceptionTest.main(ExceptionTest.java:18)
Caused by: java.util.InputMismatchException
  at java.util.Scanner.throwFor(Scanner.java:864)
  at java.util.Scanner.next(Scanner.java:1485)
  at java.util.Scanner.nextInt(Scanner.java:2117)
  at java.util.Scanner.nextInt(Scanner.java:2076)
  at practise.ExceptionTest.getInputNumbers(ExceptionTest.java:30)
  at practise.ExceptionTest.add(ExceptionTest.java:48)
  ... 1 more
*/

public class IOException extends Exception
{
  static final long serialVersionUID = 7818375828146090155L;
  public IOException()
  {
    super();
  }
  public IOException(String message)
  {
    super(message);
  }
  public IOException(String message, Throwable cause)
  {
    super(message, cause);
  }
  public IOException(Throwable cause)
  {
    super(cause);
  }
}

class Father
{
  public void start() throws IOException
  {
    throw new IOException();
  }
}
class Son extends Father
{
  public void start() throws Exception
  {
    throw new SQLException();
  }
}
/**********************假設(shè)上面的代碼是允許的（實(shí)質(zhì)是錯(cuò)誤的）***********************/
class Test
{
  public static void main(String[] args)
  {
    Father[] objs = new Father[2];
    objs[0] = new Father();
    objs[1] = new Son();
    for(Father obj:objs)
    {
    //因?yàn)镾on類拋出的實(shí)質(zhì)是SQLException，而IOException無法處理它。
    //那么這里的try。。catch就不能處理Son中的異常。
    //多態(tài)就不能實(shí)現(xiàn)了。
      try {
         obj.start();
      }catch(IOException)
      {
         //處理IOException
      }
     }
  }
}

public static void main(String[] args)
{
  int re = bar();
  System.out.println(re);
}
private static int bar()
{
  try{
    return 5;
  } finally{
    System.out.println("finally");
  }
}
/*輸出：
finally
*/

public static void main(String[] args)
{
    int result;
    result = foo();
    System.out.println(result);   /////////2
    result = bar();
    System.out.println(result);  /////////2
}
@SuppressWarnings("finally")
public static int foo()
{
    trz{
      int a = 5 / 0;
    } catch (Exception e){
      return 1;
    } finally{
      return 2;
    }
}
@SuppressWarnings("finally")
public static int bar()
{
    try {
      return 1;
    }finally {
      return 2;
    }
}

class TestException
{
  public static void main(String[] args)
  {
    int result;
    try{
      result = foo();
      System.out.println(result);      //輸出100
    } catch (Exception e){
      System.out.println(e.getMessage());  //沒有捕獲到異常
    }
    try{
      result = bar();
      System.out.println(result);      //輸出100
    } catch (Exception e){
      System.out.println(e.getMessage());  //沒有捕獲到異常
    }
  }
  //catch中的異常被抑制
  @SuppressWarnings("finally")
  public static int foo() throws Exception
  {
    try {
      int a = 5/0;
      return 1;
    }catch(ArithmeticException amExp) {
      throw new Exception("我將被忽略，因?yàn)橄旅娴膄inally中使用了return");
    }finally {
      return 100;
    }
  }
  //try中的異常被抑制
  @SuppressWarnings("finally")
  public static int bar() throws Exception
  {
    try {
      int a = 5/0;
      return 1;
    }finally {
      return 100;
    }
  }
}

class TestException
{
  public static void main(String[] args)
  {
    int result;
    try{
      result = foo();
    } catch (Exception e){
      System.out.println(e.getMessage());  //輸出：我是finaly中的Exception
    }
    try{
      result = bar();
    } catch (Exception e){
      System.out.println(e.getMessage());  //輸出：我是finaly中的Exception
    }
  }
  //catch中的異常被抑制
  @SuppressWarnings("finally")
  public static int foo() throws Exception
  {
    try {
      int a = 5/0;
      return 1;
    }catch(ArithmeticException amExp) {
      throw new Exception("我將被忽略，因?yàn)橄旅娴膄inally中拋出了新的異常");
    }finally {
      throw new Exception("我是finaly中的Exception");
    }
  }
  //try中的異常被抑制
  @SuppressWarnings("finally")
  public static int bar() throws Exception
  {
    try {
      int a = 5/0;
      return 1;
    }finally {
      throw new Exception("我是finaly中的Exception");
    }
  }
}