add ObjectUtils.defaultIfNull

Signed-off-by: Vincent Potucek <vpotucek@me.com>

Author: Vincent Potucek

spring-core/src/main/java/org/springframework/util/ObjectUtils.java

@@ -118,6 +118,48 @@ public static boolean isEmpty(@Nullable Object @Nullable [] array) {
 		return (array == null || array.length == 0);
 	}
 
+	/**
+	 * Returns the object if it is not {@code null}; otherwise, returns the default value.
+	 *
+	 * <pre>
+	 * ObjectUtils.getIfNull(null, null)      = null
+	 * ObjectUtils.getIfNull(null, "")        = ""
+	 * ObjectUtils.getIfNull(null, "zz")      = "zz"
+	 * ObjectUtils.getIfNull("abc", *)        = "abc"
+	 * ObjectUtils.getIfNull(Boolean.TRUE, *) = Boolean.TRUE
+	 * </pre>
+	 *
+	 * @param <T>          the type of the object
+	 * @param object       the object to test, may be {@code null}
+	 * @param defaultValue the default value to return if the object is {@code null}, may be {@code null}
+	 * @return {@code object} if it is not {@code null}; otherwise, {@code defaultValue}
+	 */
+	@Nullable
+	public static <T> T getIfNull(@Nullable final T object, @Nullable final T defaultValue) {
+		return Objects.nonNull(object) ? object : defaultValue;
+	}
+
+	/**
+	 * Returns the collection if it is not {@code null} and not empty; otherwise, returns the default value.
+	 *
+	 * <pre>
+	 * ObjectUtils.getIfEmpty(List.of("a"), List.of("b"))     			= List.of("a")
+	 * ObjectUtils.getIfEmpty(null, List.of("b"))            			= List.of("b")
+	 * ObjectUtils.getIfEmpty(Collections.emptyList(), List.of("b")) 	= List.of("b")
+	 * ObjectUtils.getIfEmpty(null, null)                    			= null
+	 * </pre>
+	 *
+	 * @param <T>          the type of elements in the collection
+	 * @param object       the collection to test, may be {@code null}
+	 * @param defaultValue the default value to return if the collection is {@code null} or empty, may be {@code null}
+	 * @return {@code object} if it is not {@code null} and not empty; otherwise, {@code defaultValue}
+	 */
+	@Nullable
+	public static <T> Collection<T> getIfEmpty(@Nullable final Collection<T> object,
+											   @Nullable final Collection<T> defaultValue) {
+		return Objects.nonNull(object) && !object.isEmpty() ? object : defaultValue;
+	}
+
 	/**
 	 * Determine whether the given object is empty.
 	 * <p>This method supports the following object types.

spring-core/src/test/java/org/springframework/util/ObjectUtilsTests.java

@@ -31,6 +31,7 @@
 import java.time.LocalDate;
 import java.time.ZoneId;
 import java.util.Arrays;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.Currency;
 import java.util.Date;
@@ -52,6 +53,8 @@
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
 import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+import static org.springframework.util.ObjectUtils.getIfEmpty;
+import static org.springframework.util.ObjectUtils.getIfNull;
 import static org.springframework.util.ObjectUtils.isEmpty;
 
 /**
@@ -111,6 +114,36 @@ void isCompatibleWithThrowsClause() {
 		assertThat(ObjectUtils.isCompatibleWithThrowsClause(new Throwable(), throwable)).isTrue();
 	}
 
+	@Test
+	void testGetIfNull() {
+		String value = UUID.randomUUID().toString();
+		String backup = UUID.randomUUID().toString();
+		assertThat(getIfNull(value, backup)).isEqualTo(value);
+		assertThat(getIfNull(value, value)).isEqualTo(value);
+		assertThat(getIfNull(backup, backup)).isEqualTo(backup);
+		assertThat(getIfNull(null, value)).isEqualTo(value);
+		assertThat(getIfNull(null, backup)).isEqualTo(backup);
+		assertThat(getIfNull("null", backup)).isEqualTo("null");
+		assertThat(Optional.ofNullable(getIfNull(null, null))).isEmpty();
+	}
+
+	@Test
+	void testGetIfEmpty() {
+		Collection<String> empty = Collections.emptyList();
+		Collection<String> value = List.of(UUID.randomUUID().toString());
+		Collection<String> backup = List.of(UUID.randomUUID().toString());
+		assertThat(getIfEmpty(backup, backup)).isEqualTo(backup);
+		assertThat(getIfEmpty(empty, backup)).isEqualTo(backup);
+		assertThat(getIfEmpty(value, backup)).isEqualTo(value);
+		assertThat(getIfEmpty(value, empty)).isEqualTo(value);
+		assertThat(getIfEmpty(null, backup)).isEqualTo(backup);
+		assertThat(getIfEmpty(empty, empty)).isEqualTo(empty);
+		assertThat(getIfEmpty(backup, backup)).isEqualTo(backup);
+		assertThat(getIfEmpty(null, empty)).isEqualTo(empty);
+		assertThat(getIfEmpty(null, backup)).isEqualTo(backup);
+		assertThat(Optional.ofNullable(getIfEmpty(null, null))).isEmpty();
+	}
+
 	@Test
 	void isEmptyNull() {
 		assertThat(isEmpty(null)).isTrue();