建立exception包，建立Bank类，类中有变量double  balance表示存款,Bank类的构造方法能增加存款，Bank类中有取款的发方法withDrawal(double dAmount),当取款的数额大于存款时,抛出InsufficientFundsException,取款数额为负数，抛出NagativeFundsException,如new Bank(100),表示存入银行100元，当用方法withdrawal(150)，withdrawal(-15)时会抛出自定义异常。

package Bank;public class Bank {    private static double balance;    Bank(){            };    Bank(double balance){        this.balance=balance;    }    public static void withDrawal(double dAmount) throws InsufficientFundsException,NagativeFundsException{        if(dAmount>balance){            throw new InsufficientFundsException();        }        if(dAmount<0){            throw new NagativeFundsException();        }    }    public static void main(String[] args){        Bank b=new Bank(100);        System.out.println("我有"+balance+"元存款！");        try{            withDrawal(150);        }catch(InsufficientFundsException | NagativeFundsException e){            e.printStackTrace();        }        try{            withDrawal(-15);        }catch(NagativeFundsException |InsufficientFundsException e){            e.printStackTrace();        }    }    }package Bank;public class InsufficientFundsException extends Exception {    public String getMessage(){        return "您的余额不足！";    }}package Bank;public class NagativeFundsException extends Exception{    public String getMessage(){        return "取款金额不能为负数！";    }}