'this' can only be used in non-static methods
The compiler detected use of the keyword this within a class (or static) method. Class methods are not passed implicit this references. As such, they cannot reference instance (non-static) variables or methods.
The following example illustrates this error:
public class Simple {
int x;
public static void method1() {
this.x = 12; // error: 'this' instance specific
}
}