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Simple question, simple answer:

// does this interval a intersect b?
    public boolean intersects(Interval b) {
        Interval a = this;
        if (b.left <= a.right && b.left >= a.left) { return true; }
        if (a.left <= b.right && a.left >= b.left) { return true; }
        return false;
    }

When designing a generic class which needs a parameter that is comparable you will probably end up with something like this:

public interface Page<K extends Comparable<K>>
public class LocalPage<K extends Comparable<K>> implements Page<K>

Unfortunately, using Comparable isn’t as “easy”. The Page interface described above can’t be instantiated for a type like java.sql.Time, which is not Comparable to itself, but to a supertype (i.e., java.sql.Time implements Comparable<java.util.Date>).
David Hall suggests: “If you’re going to declare types that implement Comparable, you probably need to be in the habit of writing the declaration as:”

public interface Page<K extends Comparable<? super K>>
public class LocalPage<K extends Comparable<? super K>> implements Page<K>