java value object | 易学教程

问题

I'm new to Java and I have to create a value object, (maybe it's called mapped object in Java) but my code doesn't seem to work, here is the value object:

package ....;

public class User {
    private int id;    
    private int uid;    
    private String name;

    public User()
    {
        // do something here
    }
}

and I assign a new value object like this:

public boolean some_function() 
{               
    User u = new User();

    return true; // got a breakpoint here
}

So if I comment out "User u = new User();" I will go to the breakpoint but if I keep it like above it will just stop running.

On a side note, I keep both the files in the same folder so eclipse doesn't import the file, is this correct or should I import it?

EDIT:

After some time I found out that I had to import the file manually, I thought I tried that but apparently I didn't.

回答1:

Dennis, if the code as you posted it is the exact code you're running, then this makes no sense -- the "User u = new User();" call would return you a new User object without any issues, since your constructor is empty.

To demonstrate that to yourself, change your constructor to:

public User() {
  System.out.println("I'm inside the User constructor!");
}

and call your some_function() function again. You should see that line printed out to your console.

Given what you're reporting and the code you're showing, I suspect that the class that contains some_function() isn't "seeing" the User class -- you're importing some other User class rather than the one you created. Are the two classes -- the User class and the class which contains some_function() -- in the same package? If not, what import statement at the top of the some_function()-containing class is handling the import of your User class?

回答2:

Sure you don't have an infinite loop in your User() constructor?

回答3:

Put some code into the constructor, for example

id = 99;

set a break point there.

I don't understand what you mean about importing into Eclipse - I have all my code in Eclipse - however I suspect that your application is not correctly seeing the User class. Maybe you are even getting a compilation error. Create your packages and classes in Eclipse, let it sort out the directories for you.

Show us the whole app class , including the import of User.

回答4:

Put the breakpoint on User u = new User(); and step into the constructor to see what it's doing.

来源：https://stackoverflow.com/questions/1783836/java-value-object

标签

java

value-objects