Added exists for java.

src/main/java/exists/ExistsJava.java

@@ -0,0 +1,9 @@
+package exists;
+
+import java.util.Collection;
+
+public class ExistsJava {
+	public <E> boolean exists(final Collection<E> collection, final E element) {
+		return collection.stream().anyMatch(e -> e.equals(element));
+	}
+}

src/test/java/exists/ExistsJavaTest.java

@@ -0,0 +1,25 @@
+package exists;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.Collection;
+
+public class ExistsJavaTest {
+	@Test
+	public void exists_True() {
+		final Collection<String> strings = Arrays.asList("a", "b");
+		final ExistsJava existsJava = new ExistsJava();
+		assertTrue(existsJava.exists(strings, "a"));
+	}
+
+	@Test
+	public void exists_False() {
+		final Collection<String> strings = Arrays.asList("a", "b");
+		final ExistsJava existsJava = new ExistsJava();
+		assertFalse(existsJava.exists(strings, "c"));
+	}
+}