this keyword

[Jon Wilbanks]

What is the general rule about when you should use the 'this' keyword? If I understand what I've read about it, when you create a object like:
Person p = new Person();
and then you call a method of the Person class like:
p.setFirstName("Joe");
then a 'this' pointer is sent along with the method call.
So the question is should the method be:
public void setFirstName(String s)
{
fName = s;
}
or--
public void setFirstName(String s)
{
this.fName = s;
}
Thanks for your help.

[Cindy Glass]

If you declared the variable outside the method as an instance variable you can just use fName = s;
Where the "this" comes in handy is when you try to tell the difference between a local variable and an instance variable that have the same name.
String fName;
public void setFirstName(String fName)
{
this.fName = fName;
}
Here you are telling the JVM to set the instance variable fName to the same value as the local variable fName.
Also "this" is used alot in constructors to call a different version of the overloaded constructor. For instance if you have a default constructor that calls a more complicated constructor using a bunch of default values for variables since the user didn't provide any input parameters.

class Test{
   String name;
   int age;
   public Test(){
      this("Joe Blow", 40);
   }
   public Test(String name, int age){
      this.name = name;
      this.age  = age;
   }
}

[Marilyn de Queiroz]

<font size="+0">public void setFirstName(String s)
{
     fName = s;
}
or--
public void setFirstName(String s)
{
     this.fName = s;
}

In this example the methods are equivalent. The "this" is implicit in the first case and explicit in the second.

[This message has been edited by Marilyn deQueiroz (edited May 15, 2001).]

[David O'Meara]

I alway use 'this' for getters/setters as in

private String name = null;
public void setName(String name)
{
    this.name=name;
}
public String getName()
{
    return this.name;
}

etc etc, but the thing to be really careful of is that if you spell the method parameter incorrectly then both 'name' and 'this.name' will refer to the same variable
Dave.