public abstract class Op {
    private final String name;

    private Op(String name) { this.name = name; }

    public String toString() { return name; }

    abstract boolean compareTo(int x, int y);

    public static final Op EQ = 
        new Op("=") { boolean compareTo(int x, int y) { return x == y; } };
    public static final Op NE =
        new Op("=") { boolean compareTo(int x, int y) { return x != y; } };
    public static final Op GT =
        new Op("=") { boolean compareTo(int x, int y) { return x > y; } };
    public static final Op GE =
        new Op("=") { boolean compareTo(int x, int y) { return x >= y; } };
    public static final Op LT =
        new Op("=") { boolean compareTo(int x, int y) { return x < y; } };
    public static final Op LE =
        new Op("=") { boolean compareTo(int x, int y) { return x <= y; } };
}