Creating UML for the Java code

Question

I have to create UML diagram for the two Java program/code written below. My queries are:

Is a sub class of an interface also an interface?
Is a class implementing Runnable Interface also an interface?
Can't methods/functions be called Operations of a class?
Are global variables the only attributes of a class or local variables within a function can also be called so?
In the 2nd Program the author is sending an object to the Thread constructor. Is it correct?

Aside: Can someone body please draw the UML for the two programs? I'm having hard time with understanding Threads, interface & related keywords like extends, implements.

JAVA CODE #1

public class RunThreads
  {
    public static void main(String[] args)
      {
        SomeThread p1=new new SomeThread(1);
        p1.start();
        SomeThread p2=new new SomeThread(2);
        p2.start();
        SomeThread p3=new new SomeThread(3);
        p3.start();
      }
  } // end class RunThreads

public class SomeThread extends Thread {
  {
    int myID;
    SomeThread(int id) {
      this.myID=id;
    }
    public void run() {
      int i;
      for(i = 1; i < 11; i++)
        System.out.println("Thread" + myID + ": " + i);
    }
  } // end class SomeThread

JAVA CODE #2

public class RunThreads2
  {
    public static void main(String[] args)
      {
        Thread p1 = new Thread(new SomeThread2(1));
        p1.start();
        Thread p2 = new Thread(new SomeThread2(2));
        p2.start();
        Thread p1 = new Thread(new SomeThread2(3));
        p3.start();
      }
  } // end class RunThread2

class SomeThread2 implements Runnable {
  int myID;
  SomeThread2(int id) {
    this.myID = id;
  }
  public void run() {
    int i;
    for(i=1; i<11; i++)
      System.out.println("Thread " + myID + ": " + i);
    }
  } // end class SomeThread2

_Can someone body please draw the UML for the two programs?_ - **NO**. — Rahul, Mar 21 '13 at 05:50
Pardon me if it sounded like a homework but I try to solve all the questions in my book, this was one of them. Sorry once again I'm a beginner in Java (interfaces) and UML. They are a bit confusing for me so I was expecting an answer with explanation which could help me learn in a better way. — viditkothari, Mar 21 '13 at 14:16

score 0 · Accepted Answer · answered Mar 21 '13 at 06:13

Is a sub class of an interface also an interface?

There is no such thing as a subclass of an interface. You can extend an interface with another interface, or you can implement an interface with a class.

Is a class implementing Runnable Interface also an interface?

No - it's a class. An interface is defined with interface, not class.

Can't methods/functions be called Operations of a class?

Sure - method/function/operation - sounds like reasonable synonyms to me. Internally, Java calls them Methods (see reflection related javadoc)

Are global variables the only attributes of a class or local variables within a function can also be called so?

I assume you're referring to class attributes as the objects/primitives owned by a class instance - in your first example, this would be myID in the SomeThread class. Local variables within a method are only accessible within that method (for example, i in your run method in the same class), and are not class attributes.

In the 2nd Program the author is sending an object to the Thread constructor. Is it correct?

Yes; new SomeThread2(3) returns an instance of SomeThread, which is also an object.

Can someone body please draw the UML for the two programs?

Not likely. This sounds too much like homework.

Thank you so much for the answer. Though its been a while since you posted this but its really nice to learn from your reply. — viditkothari, Mar 29 '15 at 10:23

Ameer · Answer 2 · 2013-03-21T06:22:41.543

-1

You can use IBM rational rose software to get UML diagrams for your program (it is not free version)

Or If you developed the coding then you should know the logic and you can use Edraw to draw UML diagrams.

Threads can be used only in two ways

By implementing Runnable interface or by extending Thread class.

Simple : if you use keyword extends then you using a class

if you use a keyword implements then you use an Interface.

edited Mar 21 '13 at 06:22

answered Mar 21 '13 at 06:17

Ameer

600
1
12
27

"_if you use keyword extends then you using a class_" - except for when you're [extending an interface](http://en.wikipedia.org/wiki/Interface_(Java)) – Krease Mar 21 '13 at 06:24
Interfaces can extend another interface and not a class can extend it. And his code doesn't have any abstract class. – Ameer Mar 21 '13 at 06:29
I'm not sure what abstract classes have to do with this. I was pointing out the error in your general statement. Using the keyword `extends` does not always mean you are using a class - `interface Runnable2 extends Runnable` - valid, and there are no classes being dealt with. – Krease Mar 21 '13 at 06:33

Creating UML for the Java code

2 Answers2