diff --git a/core-java/src/main/java/com/baeldung/array/ArrayInverter.java b/core-java/src/main/java/com/baeldung/array/ArrayInverter.java new file mode 100644 index 0000000000..7f7fcbb5a8 --- /dev/null +++ b/core-java/src/main/java/com/baeldung/array/ArrayInverter.java @@ -0,0 +1,41 @@ +package com.baeldung.array; + +import java.util.Arrays; +import java.util.Collections; +import java.util.List; +import java.util.stream.IntStream; + +import org.apache.commons.lang3.ArrayUtils; + +import com.google.common.collect.Lists; + +public class ArrayInverter { + + public void invertUsingFor(Object[] array) { + for (int i = 0; i < array.length / 2; i++) { + Object temp = array[i]; + array[i] = array[array.length - 1 - i]; + array[array.length - 1 - i] = temp; + } + } + + public void invertUsingCollectionsReverse(Object[] array) { + List list = Arrays.asList(array); + Collections.reverse(list); + } + + public Object[] invertUsingStreams(final Object[] array) { + return IntStream.range(1, array.length + 1).mapToObj(i -> array[array.length - i]).toArray(); + } + + public void invertUsingCommonsLang(Object[] array) { + ArrayUtils.reverse(array); + } + + public Object[] invertUsingGuava(Object[] array) { + List list = Arrays.asList(array); + List reverted = Lists.reverse(list); + return reverted.toArray(); + } + +} diff --git a/core-java/src/test/java/com/baeldung/array/ArrayInverterUnitTest.java b/core-java/src/test/java/com/baeldung/array/ArrayInverterUnitTest.java new file mode 100644 index 0000000000..ca59ee51fb --- /dev/null +++ b/core-java/src/test/java/com/baeldung/array/ArrayInverterUnitTest.java @@ -0,0 +1,49 @@ +package com.baeldung.array; + +import static org.assertj.core.api.Assertions.assertThat; + +import org.junit.Test; + +public class ArrayInverterUnitTest { + + private String[] fruits = { "apples", "tomatoes", "bananas", "guavas", "pineapples", "oranges" }; + + @Test + public void invertArrayWithForLoop() { + ArrayInverter inverter = new ArrayInverter(); + inverter.invertUsingFor(fruits); + + assertThat(new String[] { "oranges", "pineapples", "guavas", "bananas", "tomatoes", "apples" }).isEqualTo(fruits); + } + + @Test + public void invertArrayWithCollectionsReverse() { + ArrayInverter inverter = new ArrayInverter(); + inverter.invertUsingCollectionsReverse(fruits); + + assertThat(new String[] { "oranges", "pineapples", "guavas", "bananas", "tomatoes", "apples" }).isEqualTo(fruits); + } + + @Test + public void invertArrayWithStreams() { + ArrayInverter inverter = new ArrayInverter(); + + assertThat(new String[] { "oranges", "pineapples", "guavas", "bananas", "tomatoes", "apples" }).isEqualTo(inverter.invertUsingStreams(fruits)); + } + + @Test + public void invertArrayWithCommonsLang() { + ArrayInverter inverter = new ArrayInverter(); + inverter.invertUsingCommonsLang(fruits); + + assertThat(new String[] { "oranges", "pineapples", "guavas", "bananas", "tomatoes", "apples" }).isEqualTo(fruits); + } + + @Test + public void invertArrayWithGuava() { + ArrayInverter inverter = new ArrayInverter(); + + assertThat(new String[] { "oranges", "pineapples", "guavas", "bananas", "tomatoes", "apples" }).isEqualTo(inverter.invertUsingGuava(fruits)); + } + +}