Scala's tuple implmentation for Java

Tuples.java

package fupfin;

public class Tuples {
    
    private Tuples() {}
    
    public static <T1, T2> Tuple2<T1, T2> tuple(T1 v1, T2 v2) {
        return new Tuple2<T1, T2>(v1, v2);
    }

    public static <T1, T2, T3> Tuple3<T1, T2, T3> tuple(T1 v1, T2 v2, T3 v3) {
        return new Tuple3<T1, T2, T3>(v1, v2, v3);
    }
    
    public static <T1, T2, T3, T4> Tuple4<T1, T2, T3, T4> tuple(T1 v1, T2 v2, T3 v3, T4 v4) {
        return new Tuple4<T1, T2, T3, T4>(v1, v2, v3, v4);
    }

    public static class Tuple2<T1, T2> {
        public final T1 v1;
        public final T2 v2;
        
        private Tuple2(T1 v1, T2 v2) {
            this.v1 = v1;
            this.v2 = v2;
        }
    }

    public static class Tuple3<T1, T2, T3> extends Tuple2<T1, T2> {
        public final T3 v3;
        
        private Tuple3(T1 v1, T2 v2, T3 v3) {
            super(v1, v2);
            this.v3 = v3;
        }
    }
    
    public static class Tuple4<T1, T2, T3, T4> extends Tuple3<T1, T2, T3> {
        public final T4 v4;
        
        private Tuple4(T1 v1, T2 v2, T3 v3, T4 v4) {
            super(v1, v2, v3);
            this.v4 = v4;
        }
    }
}

TuplesTest.java

package fupfin;

import static org.junit.Assert.*;
import static fupfin.Tuples.*;

import org.junit.Test;


public class TuplesTest {

    @Test
    public void testTuple2() {
        Tuple2<String, Integer> result = tuple("a", 1);
        assertEquals("a", result.v1);
        assertEquals(new Integer(1), result.v2);
    }
    
    @Test
    public void testTuple3() {
        Tuple3<String, Integer, Boolean> result = tuple("a", 1, true);
        assertEquals("a", result.v1);
        assertEquals(new Integer(1), result.v2);
        assertTrue(result.v3);
    }
    
    @Test
    public void testTuple4() {
        Tuple4<String, Integer, Boolean, Float> result = tuple("a", 1, true, 0.5f);
        assertEquals("a", result.v1);
        assertEquals(new Integer(1), result.v2);
        assertTrue(result.v3);
        assertEquals(0.5, result.v4, 0.001);
    }
}