person2.java

《Java2程序设计实用教程(第2版)》课件

//【例5.5】  抛出自定义异常对象。
//【例5.6】  声明抛出异常的方法与方法调用者处理异常。

public class Person2
{
    protected String name;               //姓名
    protected int age;                   //年龄

    public Person2(String name,int age) throws Exception  //构造方法声明抛出异常
    {             //因为无法处理set()方法抛出的异常，再向上传递set()方法抛出的异常
        this.set(name);
        this.set(age);
    } 


    public void set(String name)
    {
        if (name==null || name=="")
            this.name = "姓名未知";
        else
            this.name = name;
    }
            
    public void set(int age) throws Exception    //声明方法抛出异常
    {
        if (age>=0 && age<100)
            this.age = age;
        else
            throw new Exception("IllegalAgeData: "+age); 
    }

    public void set(String name, int age) throws Exception
    {
        this.set(name);
        this.set(age);
    }
            
    public String toString() 
    {
        return this.name+","+this.age+"岁";
    }
    
    public void print()
    {
        System.out.println(this.toString());
    }

    public static void main(String args[]) throws Exception
    {
        Person2 p1 = new Person2("李小明",20);
        p1.print();
            
        p1.set(121);
        p1.print();
    }
}

/* 
程序运行结果如下：

李小明,20岁
Exception in thread "main" java.lang.Exception: IllegalAgeData: 121
            at Person2.set(Person2.java:29)
            at Person2.main(Person2.java:53)


*/


/*        

    public Person2(String name) throws Exception
    {
        this(name,0);
    } 
    
    public Person2() throws Exception
    {
        this("姓名未知",0);
    }
     
    public Person2(Person2 p1) throws Exception 
    {
        this(p1.name, p1.age);
    }
    
    public void set(int age)       //原始
    {
        if (age>0 && age<100)
            this.age = age;
        else
            this.age = 0;
    }

    public void set(int age)
    {
        if (age>0 && age<100)
            this.age = age;
        else
            throw new Exception("IllegalAgeData"); //抛出异常
    }

    public void set(int age)
    {
        try
        {
            if (age>0 && age<100)
                this.age = age;
            else
                throw new Exception("IllegalAgeData"); //抛出异常
        }
        catch(Exception e)
        {
            System.out.println(e.toString());    //虽然捕获到了异常但不能处理，this.age仍没有值
        }
    }
    
    public void set(Person2 p1)  throws Exception
    {
        this.set(p1.name);
        this.set(p1.age);
    }
            
    public static void main(String args[])
    {
        try
        {
            Person2 p1 = new Person2("李小明",20);  //调用声明将抛出异常的方法，必须写在try语句中，否则编译不通过
            p1.print();
            
            p1.set(121);
            p1.print();
        }
        catch(Exception e)
        {
            System.out.println(e.toString());      //捕获到了异常
        }
    }


程序运行结果如下：

李小明,20岁
java.lang.Exception: IllegalAgeData: 121

    
*/