求高手写一个判断数字是否为double类型的抛出异常Exception,给全分谢谢

[changeking]

就是自定义异常,创建了这个异常类以后就可以直接调用这个异常了,
拜托了

[loveofmylife]

public class MyException extends Exception{
	public MyException()  {}
    public MyException(String message) {
        super(message);
    }
}

不明白LZ什么意思，自定义异常不就是这样吗

[justinavril]

最简单的：

import java.lang.reflect.*;

class DoubleException extends Exception{
	public String toString(){
		return "It's not a double value!";
	}
}

public class IsDouble{
	double d = 1.0;
	int j = 1;
	
	public static void main(String args[]){	
		try{
			Class c = Class.forName("IsDouble");			
			Field fieldlist[] = c.getDeclaredFields();  

	        for (int i = 0; i < fieldlist.length; i++) {  
	        	Field fld = fieldlist[i];  
	        	
	            if(fld.getType().getName().equals("double")) 
	            	throw new DoubleException();            
	            else
	            	System.out.println(fld.getName() +": "+ fld.getType());
	        }
		}catch (Exception e) {  
	           e.printStackTrace();  
	    } 
	}
}

输出：

It's not a double value!
	at IsDouble.main(IsDouble.java:22)

[rookie001]

自定义异常 楼上已有

何时抛：
double d = 1.0;
Double d = new Double(d);
if(d instanceof Double) throw new DoubleException();

[lz12366]

顶上面的。。。

[loveofmylife]

public class IsDouble {
	public static boolean isDou(Number n){
		boolean b=false;
			try {
				b=Class.forName("java.lang.Double").isInstance(n);
			} catch (ClassNotFoundException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			if(!b){
				try {
					throw new MyException("is not a Double");
				} catch (MyException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		return b;
	}
	public static void main(String[] args){
		Double d=1.0;
		int i=1;
		System.out.println(isDou(d));
		System.out.println(isDou(i));
	}
}

测试结果：true
day05.MyException: is not a Double
at day05.IsDouble.isDou(IsDouble.java:14)
at day05.IsDouble.main(IsDouble.java:26)
false
就用我1楼的那个异常

[jayqean]

[Quote=引用 5 楼 viszl 的回复:]
Java codepublicclass IsDouble {publicstaticboolean isDou(Number n){boolean b=false;try {
b=Class.forName("java.lang.Double").isInstance(n);
}catch (ClassNotFoundException e) {// TODO Auto-generated catch block e.printStackTrace();
}if(!b){try {thrownew MyException("is not a Double");
}catch (MyException e) {// TODO Auto-generated catch block e.printStackTrace();
}
}return b;
}publicstaticvoid main(String[] args){
Double d=1.0;int i=1;
System.out.println(isDou(d));
System.out.println(isDou(i));
}
}
测试结果：true
day05.MyException: is not a Double
at day05.IsDouble.isDou(IsDouble.java:14)
at day05.IsDouble.main(IsDouble.java:26)
false
就用我1楼的那个异常
[/Quote]
顶

[dzlldxz]

学习了 。。。 当做复习了 。。。。

[liuc0317]

自定义异常！不 就是定义一个自己的异常！用来extends 非受检异常!最终的目的是不受检异常转化成
非受检异常！
public class MyException extends RuntimeException{


private static final long serialVersionUID = -1663367068727673091L;

public DAOException() {
super();
// TODO Auto-generated constructor stub
}

public DAOException(String message, Throwable cause) {
super(message, cause);
// TODO Auto-generated constructor stub
}

public DAOException(String message) {
super(message);
// TODO Auto-generated constructor stub
}

public DAOException(Throwable cause) {
super(cause);
// TODO Auto-generated constructor stub
}


}

[火龙果被占用了]

我不是很明白，如果你把方法参数设定为 public void test(double num); 这样的话，还有必须去判断 num 是 double 类型么？

[lz12366]

2#把异常放错地方了吧？？？

import java.lang.reflect.*;

class DoubleException extends Exception
{

private static final long serialVersionUID = 1L;

public String toString(){
return "It's not a double value!";
}
}

public class IsDouble{
double d = 1.0;
int j = 1;

public static void main(String args[]){
try{
Class<?> c = Class.forName("IsDouble");
Field fieldlist[] = c.getDeclaredFields();

for (int i = 0; i < fieldlist.length; i++) {
Field fld = fieldlist[i];

if(fld.getType().getName().equals("double"))
System.out.println(fld.getName() +": "+ fld.getType());
else
throw new DoubleException();
}
}catch (Exception e) {
e.printStackTrace();
}
}
}

这样才能判断类中所有的变量是不是double类型