Initial value of object reference defined as instance variable

package com.javahonk.stringtest;

public class ObjectInstanceTest {

    TopClass topClass;

    public static void main(String[] args) {

	ObjectInstanceTest objectInstanceTest = new ObjectInstanceTest();
	System.out.println(objectInstanceTest.topClass);

    }
}

class TopClass {
    private String str;

    public String getStr() {
	return str;
    }

    public void setStr(String str) {
	this.str = str;
    }

}