Java tutorial
//package com.java2s; import java.util.*; public class Main { public static void assertAllDifferent(Object... entities) { assertAllDifferent(Arrays.asList(entities)); } public static void assertAllDifferent(List<?> entities) { Set<?> set = new LinkedHashSet<>(entities); if (set.size() != entities.size()) { throw new IllegalArgumentException("All entities must be different: " + entities + ", " + set); } } }