Example for removing first element of array (BAEL-2029) (#4836)

* Example for removing first element of array (BAEL-2029)

* Use AssertJ assertions

core-java/src/test/java/com/baeldung/array/RemoveFirstElementUnitTest.java

@@ -0,0 +1,42 @@
+package com.baeldung.array;
+
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class RemoveFirstElementUnitTest {
+
+    @Test
+    public void givenStringArray_whenRemovingFirstElement_thenArrayIsSmallerAndElementRemoved() {
+        String[] stringArray = {"foo", "bar", "baz"};
+
+        String[] modifiedArray = Arrays.copyOfRange(stringArray, 1, stringArray.length);
+
+        assertThat(modifiedArray.length).isEqualTo(2);
+        assertThat(modifiedArray[0]).isEqualTo("bar");
+    }
+
+    @Test
+    public void givenArrayList_whenRemovingFirstElement_thenListSmallerAndElementRemoved() {
+        List<String> stringList = new ArrayList<>(Arrays.asList("foo", "bar", "baz"));
+        stringList.remove(0);
+
+        assertThat(stringList.size()).isEqualTo(2);
+        assertThat(stringList.get(0)).isEqualTo("bar");
+    }
+
+    @Test
+    public void givenLinkedList_whenRemovingFirstElement_thenListSmallerAndElementRemoved() {
+        List<String> stringList = new LinkedList<>(Arrays.asList("foo", "bar", "baz"));
+        stringList.remove(0);
+
+        assertThat(stringList.size()).isEqualTo(2);
+        assertThat(stringList.get(0)).isEqualTo("bar");
+    }
+
+}