我们什么时候应该在 Java 中创建用户定义的异常类?
javaobject oriented programmingprogramming更新于 2024/7/26 5:33:00
我们应该在 Java 中创建自己的异常。编写自己的异常类时，请牢记以下几点
- 所有异常都必须是 Throwable 的子类。
- 如果我们想编写由 Handle 或 Declare 规则自动执行的已检查异常，则需要扩展 Exception 类。
- 如果我们想编写运行时异常，则需要扩展 RuntimeException 类。
我们可以定义自己的 Exception 类，如下所示:
class MyException extends Exception {
}
我们只需扩展 Exception 类即可创建自己的 Exception 类。这些被视为已检查异常。以下 InsufficientFundsException 类是用户定义的异常，它扩展了 Exception 类，使其成为已检查的异常。
示例
// File Name InsufficientFundsException.java
import java.io.*;
class InsufficientFundsException extends Exception {
private double amount;
public InsufficientFundsException(double amount) {
this.amount = amount;
}
public double getAmount() {
return amount;
}
}
// File Name CheckingAccount.java
class CheckingAccount {
private double balance;
private int number;
public CheckingAccount(int number) {
this.number = number;
}
public void deposit(double amount) {
balance += amount;
}
public void withdraw(double amount) throws InsufficientFundsException {
if(amount <= balance) {
balance -= amount;
}
else {
double needs = amount - balance;
throw new InsufficientFundsException(needs);
}
}
public double getBalance() {
return balance;
}
public int getNumber() {
return number;
}
}
// File Name BankDemo.java
public class BankDemo {
public static void main(String [] args) {
CheckingAccount c = new CheckingAccount(101);
System.out.println("Depositing $500...");
c.deposit(500.00);
try {
System.out.println("\nWithdrawing $100...");
c.withdraw(100.00);
System.out.println("\nWithdrawing $600...");
c.withdraw(600.00);
} catch(InsufficientFundsException e) {
System.out.println("Sorry, but you are short $" + e.getAmount());
e.printStackTrace();
}
}
}
输出
Depositing $500... Withdrawing $100... Withdrawing $600... Sorry, but you are short $200.0 InsufficientFundsException at CheckingAccount.withdraw(BankDemo.java:32) at BankDemo.main(BankDemo.java:53)
