Hidden Features of Java

Answer 1

Using this keyword for accessing fields/methods of containing class from an inner class. In below, rather contrived example, we want to use sortAscending field of container class from the anonymous inner class. Using ContainerClass.this.sortAscending instead of this.sortAscending does the trick.

import java.util.Comparator;

public class ContainerClass {
boolean sortAscending;
public Comparator createComparator(final boolean sortAscending){
    Comparator comparator = new Comparator() {

        public int compare(Integer o1, Integer o2) {
            if (sortAscending || ContainerClass.this.sortAscending) {
                return o1 - o2;
            } else {
                return o2 - o1;
            }
        }

    };
    return comparator;
}
}