8138963: java.lang.Objects new method to default to non-null
Summary: add java.util.Object.nonNullElse and nonNullElseGet
Reviewed-by: dfuchs, jrose, psandoz, smarks, igerasim, chegar
--- a/jdk/src/java.base/share/classes/java/util/Objects.java Tue Oct 20 17:15:00 2015 -0700
+++ b/jdk/src/java.base/share/classes/java/util/Objects.java Wed Oct 21 14:18:49 2015 -0400
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2009, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2009, 2015, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@@ -282,6 +282,43 @@
}
/**
+ * Returns the first argument if it is non-{@code null} and
+ * otherwise returns the non-{@code null} second argument.
+ *
+ * @param obj an object
+ * @param defaultObj a non-{@code null} object to return if the first argument
+ * is {@code null}
+ * @param <T> the type of the reference
+ * @return the first argument if it is non-{@code null} and
+ * otherwise the second argument if it is non-{@code null}
+ * @throws NullPointerException if both {@code obj} is null and
+ * {@code defaultObj} is {@code null}
+ * @since 9
+ */
+ public static <T> T nonNullElse(T obj, T defaultObj) {
+ return (obj != null) ? obj : requireNonNull(defaultObj, "defaultObj");
+ }
+
+ /**
+ * Returns the first argument if it is non-{@code null} and otherwise
+ * returns the non-{@code null} value of {@code supplier.get()}.
+ *
+ * @param obj an object
+ * @param supplier of a non-{@code null} object to return if the first argument
+ * is {@code null}
+ * @param <T> the type of the first argument and return type
+ * @return the first argument if it is non-{@code null} and otherwise
+ * the value from {@code supplier.get()} if it is non-{@code null}
+ * @throws NullPointerException if both {@code obj} is null and
+ * either the {@code supplier} is {@code null} or
+ * the {@code supplier.get()} value is {@code null}
+ * @since 9
+ */
+ public static <T> T nonNullElseGet(T obj, Supplier<? extends T> supplier) {
+ return (obj != null) ? obj : requireNonNull(requireNonNull(supplier, "supplier").get(), "supplier.get()");
+ }
+
+ /**
* Checks that the specified object reference is not {@code null} and
* throws a customized {@link NullPointerException} if it is.
*
--- a/jdk/test/java/util/Objects/BasicObjectsTest.java Tue Oct 20 17:15:00 2015 -0700
+++ b/jdk/test/java/util/Objects/BasicObjectsTest.java Wed Oct 21 14:18:49 2015 -0400
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2009, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2009, 2015, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@@ -44,6 +44,7 @@
errors += testRequireNonNull();
errors += testIsNull();
errors += testNonNull();
+ errors += testNonNullOf();
if (errors > 0 )
throw new RuntimeException();
}
@@ -232,4 +233,46 @@
return errors;
}
+
+ private static int testNonNullOf() {
+ int errors = 0;
+ String defString = new String("default");
+ String nullString = null;
+ String nonNullString = "non-null";
+
+ // Confirm the compile time return type matches
+ String result = Objects.nonNullElse(nullString, defString);
+ errors += (result == defString) ? 0 : 1;
+ errors += (Objects.nonNullElse(nonNullString, defString) == nonNullString) ? 0 : 1;
+ errors += (Objects.nonNullElse(nonNullString, null) == nonNullString) ? 0 : 1;
+ try {
+ Objects.nonNullElse(null, null);
+ errors += 1;
+ } catch (NullPointerException npe) {
+ // expected
+ errors += npe.getMessage().equals("defaultObj") ? 0 : 1;
+ }
+
+
+ // Test nonNullElseGet with a supplier
+ errors += (Objects.nonNullElseGet(nullString, () -> defString) == defString) ? 0 : 1;
+ errors += (Objects.nonNullElseGet(nonNullString, () -> defString) == nonNullString) ? 0 : 1;
+ errors += (Objects.nonNullElseGet(nonNullString, () -> null) == nonNullString) ? 0 : 1;
+
+ try {
+ Objects.nonNullElseGet(null, () -> null);
+ errors += 1;
+ } catch (NullPointerException npe) {
+ // expected
+ errors += npe.getMessage().equals("supplier.get()") ? 0 : 1;
+ }
+ try { // supplier is null
+ Objects.nonNullElseGet(null, null);
+ errors += 1;
+ } catch (NullPointerException npe) {
+ // expected
+ errors += npe.getMessage().equals("supplier") ? 0 : 1;
+ }
+ return errors;
+ }
}