System.out.println(Set); what does it prints actually????

[ankur trapasiya]

here is my code

class B
{
	private String name;
	B(String name )
	{
		this.name=name;
	}
	public int hashCode()
	{
		return 1;
	}
	public boolean equals(Object o)
	{
		if(o instanceof B && ((B)o).name.equals(this.name))
		{
			return true;
		}
		return false;
	}
}
public class SetTest
{
	public static void main(String[] args)
	{
                Set b3=new HashSet();
		boolean p[]=new boolean[3];
		p[0]=b3.add(new B("a"));
		p[1]=b3.add(new B("a"));
		p[2]=b3.add(new B("c"));
		System.out.println("after implementing equals");
		for(boolean b1: p)
		{
			System.out.println(b1);
		}
		System.out.println("Set3  :- " + b3.contains(new B("c")) + " set3" + b3);
         }
}

and the output is

after implementing equals
true
false
true
Set3:- true set3[B@1,B@1]


my question is what does B@1 mean??? and why it is not printing the entire set like Lists ???

[Ankit Garg]

It is printing the entire contents of the Set. Your Set contains two elements and on both elements it calls the toString method of class B. Since you have not overridden the toString method in class B so the toString method of Object class will be invoked which returns <ClassName>@<hashCode> so you get the output B@1 for each element in the Set...

[Andrew Monkhouse]

ankur trapasiya wrote:and why it is not printing the entire set like Lists ???

Part of your problem is that you are trying multiple things at once, and therefore not understanding the results you are getting. Printing the set does print the contents, as the following example shows:

import java.util.*;

public class SetTest {
    public static void main(String[] args) {
        Set<Integer> b3 = new HashSet<Integer>();
        b3.add(4);
        b3.add(12);
        System.out.println("Set3  :- " + b3);
    }
}

Try this - does it provide the result you expect?

Given that, can you think of why your code is different / an alternate question to go from here?

[ankur trapasiya]

thanks ankit and andrew....my doubt got cleared.....