异常简单理解

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throw 和throws

throw 抛出异常，throws 声明异常。

class InsufficientFundsException extends Exception{   private Bank  excepbank;      // 银行对象   private double excepAmount;   // 要取的钱   InsufficientFundsException(Bank ba, double  dAmount)    {  excepbank=ba;       excepAmount=dAmount;   }   public String excepMessage(){     String  str="The balance is"+excepbank.balance       + "\n"+"The withdrawal was"+excepAmount;     return str;    }}// 异常类

class Bank{   double balance;// 存款数   Bank(double  balance){this.balance=balance;}   public void deposite(double dAmount){    if(dAmount>0.0) balance+=dAmount;   }   public void withdrawal(double dAmount)               throws  InsufficientFundsException{    if (balance<dAmount)     throw new          InsufficientFundsException(this, dAmount);//throw 抛出异常      balance=balance-dAmount;   }   public void showBalance(){      System.out.println("The balance is "+(int)balance);   }}

public class ExceptionDemo{   public static void main(String args[]){    try{       Bank ba=new Bank(50);          ba.withdrawal(100);          System.out.println("Withdrawal successful!");      }catch(InsufficientFundsException e) {    //catch  捕获异常  ，对应throw 抛出          System.out.println(e.toString());     //这是捕获之后的处理          System.out.println(e.excepMessage());      }   }}

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