### Question:
Pair { @Override public String toString() { return toString("(", ",", ")"); } Pair(A f, B s); @Override int hashCode(); @Override boolean equals(Object o); A getFirst(); B getSecond(); @Override String toString(); String toString(String prefix, String separator, String suffix); Entry<A,B> toMapEntry(); Pair<B,A> swap(); static Pair<K2,V2> fromEntry(Entry<K1,V1> entry);  }### Answer:
@Test public void testToString() { Pair<Integer,String> pair = new Pair<>(25, "twenty-five"); assertEquals("(25,twenty-five)", pair.toString()); }
@Test public void testToStringStringStringString() { Pair<Integer,String> pair = new Pair<>(25, "twenty-five"); assertEquals("---25~~~twenty-five+++", pair.toString("---", "~~~", "+++")); }