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Add emulation for Java 9 additions to Objects class #10107

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cfd11b6
Add emulation for Java 9 additions to Objects class
zbynek Mar 25, 2025
4ce70ae
Apply suggestions from code review
zbynek Mar 25, 2025
5c1cdfc
Add tests and comment
zbynek Mar 29, 2025
b1acf4f
Merge branch 'main' of https://github.com/gwtproject/gwt into java11-…
zbynek May 1, 2025
9d6de8e
Throw the right exception
zbynek May 1, 2025
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32 changes: 32 additions & 0 deletions user/super/com/google/gwt/emul/java/util/Objects.java
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Original file line number Diff line number Diff line change
Expand Up @@ -129,6 +129,38 @@ public static <T> T requireNonNull(T obj, Supplier<String> messageSupplier) {
return obj;
}

public static <T> T requireNonNullElse(T obj, T defaultObj) {
return obj != null ? obj : requireNonNull(defaultObj);
}

public static <T> T requireNonNullElseGet(T obj, Supplier<? extends T> supplier) {
return obj != null ? obj : requireNonNull(requireNonNull(supplier, "supplier").get());
}

public static int checkIndex(int index, int length) {
if (index < 0 || index >= length) {
throw new IndexOutOfBoundsException("Index " + index + " out of bounds for length " + length);
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I'm unsure about this exception message. Can't remember if it'll be pruned in production builds (in which case this is OK) or not (in which case we should just throw the exception without message)

Alternatively, we could emulate the IndexOufOfBoundsException(int) constructor and use it here.

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@niloc132 niloc132 Mar 26, 2025 •
edited
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I think if we are exposing user methods to call, we should leave it up to them to prune or not - GWT might prune null checks inside of collections and such if directed, but we wouldn't want to actually rewrite if (foo == null) etc, and likewise shouldn't optimize these out?

EDIT: you're specifically talking about the error message being pruned, while I'm speaking more broadly, the runtime error at all, and the expected error message (which the developer explicitly wants).

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The information should be transported to the user. Some months ago I came across an IOOBE in GWT which did not provide any information and it was annoying.

GWT already has a bunch of different exception messages for IOOBE so I am fine with the text.

I guess we would save more if GWT would provide some internal ctors or factory methods in IOOBE each providing a fixed, short error message and then use these ctors everywhere to get rid of all the different messages.

}
return index;
}

public static int checkFromToIndex(int fromIndex, int toIndex, int length) {
if (fromIndex < 0 || fromIndex > toIndex || toIndex > length) {
throw new IndexOutOfBoundsException("Range [" + fromIndex + ", " + toIndex
+ ") out of bounds for length " + length);
}
return fromIndex;
}

public static int checkFromIndexSize(int fromIndex, int size, int length) {
// in JS fromIndex + size cannot overflow because int is not limited to 32 bits
if (fromIndex < 0 || size < 0 || fromIndex + size > length) {
throw new IndexOutOfBoundsException("Range [" + fromIndex + ", " + (fromIndex + size)
+ ") out of bounds for length " + length);
}
return fromIndex;
}

public static String toString(Object o) {
return String.valueOf(o);
}
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74 changes: 74 additions & 0 deletions user/test/com/google/gwt/emultest/java/util/ObjectsTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -102,4 +102,78 @@ public void testHashCode() {
Object obj = new Object();
assertEquals(obj.hashCode(), Objects.hashCode(obj));
}

public void testRequireNonNull() {
assertEquals("foo", Objects.requireNonNull(hideFromCompiler("foo")));
assertThrows(NullPointerException.class,
() -> Objects.requireNonNull(hideFromCompiler(null)));
}

public void testRequireNonNullElse() {
assertEquals("foo", Objects.requireNonNullElse(hideFromCompiler("foo"), "bar"));
assertEquals("bar", Objects.requireNonNullElse(hideFromCompiler(null), "bar"));
assertThrows(NullPointerException.class,
() -> Objects.requireNonNullElse(hideFromCompiler(null), null));
}

public void testRequireNonNullElseGet() {
assertEquals("foo",
Objects.requireNonNullElseGet(hideFromCompiler("foo"), () -> "bar"));
assertEquals("bar",
Objects.requireNonNullElseGet(hideFromCompiler(null), () -> "bar"));
assertThrows(NullPointerException.class,
() -> Objects.requireNonNullElseGet(hideFromCompiler(null), null));
assertThrows(NullPointerException.class,
() -> Objects.requireNonNullElseGet(hideFromCompiler(null), () -> null));
}

private String hideFromCompiler(String value) {
if (Math.random() > 2) {
return "unreachable";
}
return value;
}

public void testCheckIndex() {
assertEquals(5, Objects.checkIndex(5, 10));
assertThrows(IndexOutOfBoundsException.class,
() -> Objects.checkIndex(-5, 5));
assertThrows(IndexOutOfBoundsException.class,
() -> Objects.checkIndex(10, 5));
assertThrows(IndexOutOfBoundsException.class,
() -> Objects.checkIndex(5, 5));
}

public void testCheckFromToIndex() {
assertEquals(5, Objects.checkFromToIndex(5, 7, 10));
assertEquals(0, Objects.checkFromToIndex(0, 10, 10));
assertThrows(IndexOutOfBoundsException.class,
() -> Objects.checkFromToIndex(-5, 1, 5));
assertThrows(IndexOutOfBoundsException.class,
() -> Objects.checkFromToIndex(10, 1, 5));
assertThrows(IndexOutOfBoundsException.class,
() -> Objects.checkFromToIndex(1, 10, 5));
}

public void testCheckFromIndexSize() {
assertEquals(5, Objects.checkFromIndexSize(5, 2, 10));
assertEquals(0, Objects.checkFromIndexSize(0, 10, 10));
assertThrows(IndexOutOfBoundsException.class,
() -> Objects.checkFromIndexSize(-5, 1, 5));
assertThrows(IndexOutOfBoundsException.class,
() -> Objects.checkFromIndexSize(10, 1, 5));
assertThrows(IndexOutOfBoundsException.class,
() -> Objects.checkFromIndexSize(1, 10, 5));
assertThrows(IndexOutOfBoundsException.class,
() -> Objects.checkFromIndexSize(1, -5, 5));
}

private void assertThrows(Class<? extends Exception> thrownCheck, Runnable toTest) {
try {
toTest.run();
fail("Should have failed");
} catch (Exception ex) {
assertEquals(thrownCheck, ex.getClass());
}
}
}