java double判断是否为空,检查double值是否为null（如果在Bean类中设置double值）

I have created a Java bean class like this

class BeanDemo

{

private double value;

//getter and setter

}

class myApp

{

BeanDemo beanDemo=new BeanDemo();

int val=7;

if(val<5)

{

beanDemo.setValue(23.456);

}

double value=beanDemo.getValue(); // Always returns 0.0 if it is not set

System.out.println(value);

}

How can I check if that value is null? I mean if it is not set I should print something else(say null)

I cannot check if its 0.0 because may be i can set the value to 0.0 also.

Thanks

解决方案

It sounds like you should be using Double (the class) rather than double (the primitive). There's no such thing as a null value of type double:

class BeanDemo {

private Double value;

public void setValue(Double value) {

this.value = value;

}

public Double getValue() {

return value;

}

}

class Test {

public static void main(String[] args) {

BeanDemo beanDemo = new BeanDemo();

int val=7;

if (val < 5) {

beanDemo.setValue(23.456);

}

Double value = beanDemo.getValue(); // value will be null

System.out.println(value);

}

}

Note that you could make your setter take double instead of Double if you wanted to prevent it from becoming null again after being set once.