Generate MD5 hash in Java

Is there any method to generate MD5 hash of a string in Java?

Why is it important to override GetHashCode when Equals method is overriden in C#?

Given the following class

public class Foo

{

    public int FooId { get; set; }

    public string FooName { get; set; }



    public override bool Equals(object obj)

    {

        Foo fooItem = obj as Foo;



        return fooItem.FooId == this.FooId;

    }



    public override int GetHashCode()

    {

        // Which is preferred?



        return base.GetHashCode();



        //return this.FooId.GetHashCode();

    }

}

What is a sensible prime for hashcode calculation?

Eclipse 3.5 has a very nice feature to generate Java hashCode() functions. It would generate for example (slightly shortened:)

apache commons equals/hashcode builder

I'm curious to know, what people here think about using org.apache.commons.lang.builder EqualsBuilder/HashCodeBuilder for implementing the equals/hashcode? Would it be a better practice than writing your own? Does it play well with Hibernate? What's your opinion?