That isn't Javascript: it's Java. Please tag your posts with the correct language ... it makes our job a lot easier and that means you get better results.
Private_String
isn't declared anywhere there, and I'd guess that it's not what you wanted.
Try this:
private String name;
private Int age;
public Person()
{
name = "Raju";
age = 22;
}
public void talk()
{
System.out.println("hello my name is" + name);
System.out.println("my age is" + age);
}