Java program will compile but not run

Question

I was wondering if someone could help me with this.

I have defined my interface as:

interface Model 
{
public String  toString();
public Model add (Model m);
}

There are 2 classes implementing the interface (ClassA and ClassB):

class ClassA implements Model
{
private int val;

public ClassA(int x) 
{
    val = x;
}

public String toString() 
{
 return ""+ "value of object of class A is " + val;
}

public Model add (Model m) 
{
 if (m instanceof ClassA)
   return new ClassA(val + ( (ClassA) m).val);
 else
   return null;
}
}

class ClassB implements Model 
{

private String str;

public  ClassB(String s)
{
 str = s;
}

public String toString()
{
 return str;
 }

 public Model add (Model m) 
 {
 if (m instanceof ClassB)                      
 return new ClassB(str + ((ClassB) m).str); 
 else
 return null;
 }
 }

My main defines objects of ClassA and ClassB and calls their tostring() methods.

public class Example {
public static void main (String args[]) {
 ClassA a = new ClassA(5);
 ClassB b= new ClassB("Hi");

 Model m = b;
 System.out.println(m.toString());

 ClassA a1 = new ClassA(7);

 m = a.add(a1);

 System.out.println(m);
}
}

When I try to build this file it compiles fine but, upon trying to run the application I get an error message:

"Usage: java [-options] class [args...] (to execute a class) or java [-options] -jar jarfile [args...] (to execute a jar file).....etc...etc"

Can anyone help me with this? It's probably something simple. I'm a beginner Java student.

What may be most important is what you're not showing us. How are you trying to run this program? — Hovercraft Full Of Eels
– Hovercraft Full Of Eels, Commented Apr 7, 2012 at 2:56
What command are you typing when you try to run your program? What command did you use to compile it? — Mark Byers
– Mark Byers, Commented Apr 7, 2012 at 2:56
Can you write the command you launch when you try run the application? — dash1e
– dash1e, Commented Apr 7, 2012 at 2:57
I am using JCreator and clicking on the "run file" option after building file. — dRock
– dRock, Commented Apr 7, 2012 at 2:58
Trying compiling and running it in terminal or command prompt with javac Example.java to compile and java Example to run it. Then tell us what happens. (Make sure you are in the right directory) — Jon Egeland
– Jon Egeland, Commented Apr 7, 2012 at 2:59

delavega66 · Accepted Answer · 2015-05-22 13:50:08Z

1

There is no error in your program.Your program is absolutely ok. But , I do not know which command you are writing for execution .Try once again with absolute path setting to JDK and JRE.

Command like:-

for Compile -javac Example.java for Run -java Example

It will successfully run. Hope it will help you.

edited May 22, 2015 at 13:50

delavega66

9842 gold badges24 silver badges42 bronze badges

answered Apr 7, 2012 at 3:47

JDGuide

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