The this keyword is primarily used in three situations. The first and most common is in setter methods to disambiguate variable references. The second is when there is a need to pass the current class instance as an argument to a method of another object. The third is as a way to call alternate constructors from within a constructor.
In Java setter methods, we commonly pass in an argument with the same name as the private member variable we are attempting to set. We then assign the argument x to this.x. This makes it clear that you are assigning the value of the parameter “name” to the instance variable “name”.
public class Foo
{
private String name;
public void setName(String name) {
this.name = name;
}
}
public class Foo
{
public String useBarMethod() {
Bar theBar = new Bar();
return theBar.barMethod(this);
}
public String getName() {
return "Foo";
}
}
public class Bar
{
public void barMethod(Foo obj) {
obj.getName();
}
}
When you have multiple constructors for a single class, you can use this(arg0, arg1, …) to call another constructor of your choosing, provided you do so in the first line of your constructor.
class Foo
{
public Foo() {
this("Some default value for bar");
//optional other lines
}
public Foo(String bar) {
// Do something with bar
}
}
I have also seen this used to emphasize the fact that an instance variable is being referenced (sans the need for disambiguation), but that is a rare case in my opinion.