Use Java Language.

// A StringSet is a collection of non-null strings, with no duplicates

// (i.e., no two elements may be equal).

public class StringSet {

private

public StringSet() {

}

// Throws an IllegalArgumentException if e is null, otherwise adds

// e to the set if there is not already an element in the set equal

// to e

public void insert(String e) {

}

// Throws an IllegalArgumentException if e is null, otherwise

// indicates whether the set contains e

public boolean contains(String e) {

}