//DivideByZeroException.java public class DivideByZeroException extends ArithmeticException ( public DivideByZeroException()l super("Attempted to divide by zero"); //DivideByZeroExceptionTester.java public class DivideByZeroExceptionTester ( private static int quotient(int numerator, int denominator) .throws DivideByZeroException ( if (denominator == 0) throw new DivideByZeroException();return(numerator / denominator); public static yoid main(String args[]) int numberl=0, number2=0, result=0; tryl System.out.println("Enter the first number:"); numberl = Integer.valueof(Keyboard.getString()).intValue(): System.out.println("Enter the second number:"); number2= Integer.valueof(Keyboard.getString()).intvalue(); result = quotient (number1, number2); catch (NumberFormatException e) System.out.println("Invalid integer entered!")i System.exit(-1); catch (DivideByZeroException e) System.out.println(e.toString()): System.exit(-1); System.out.println(numberl + "/ "+ number2 + "="+ result);解释每一句话

//DivideByZeroException.java
//定义了一个继承自ArithmeticException的异常类DivideByZeroException
public class DivideByZeroException extends ArithmeticException {
public DivideByZeroException() {
super("Attempted to divide by zero");
}
}

//DivideByZeroExceptionTester.java
public class DivideByZeroExceptionTester {
//定义了一个可以抛出DivideByZeroException异常的方法quotient，用于计算两个整数的商
private static int quotient(int numerator, int denominator) throws DivideByZeroException {
if (denominator == 0) {
//如果分母为0，则抛出DivideByZeroException异常
throw new DivideByZeroException();
}
return (numerator / denominator);
}

public static void main(String args[]) {
int number1 = 0, number2 = 0, result = 0;
try {
//尝试从键盘读取两个整数
System.out.println("Enter the first number:");
number1 = Integer.valueOf(Keyboard.getString()).intValue();
System.out.println("Enter the second number:");
number2 = Integer.valueOf(Keyboard.getString()).intValue();
//计算结果
result = quotient(number1, number2);
} catch (NumberFormatException e) {
//如果输入的不是整数，则捕获异常并输出错误信息
System.out.println("Invalid integer entered!");
System.exit(-1);
} catch (DivideByZeroException e) {
//如果出现了除以0的情况，则捕获异常并输出错误信息
System.out.println(e.toString());
System.exit(-1);
}
//输出结果
System.out.println(number1 + " / " + number2 + " = " + result);
}
}

以上代码的作用是：从键盘读取两个整数，计算它们的商并输出结果，如果出现了除以0的情况或输入的不是整数，则会捕获相应的异常并输出错误信息。