8215401: Add isEmpty default method to CharSequence
Reviewed-by: jlaskey, rriggs, jjg, alanb, smarks, darcy
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parent
7d330d34f1
commit
113c48f5da
src/java.base/share/classes/java
test/jdk/java/lang/CharSequence
@ -1,5 +1,5 @@
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/*
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* Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.
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* Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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@ -87,6 +87,21 @@ public interface CharSequence {
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*/
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char charAt(int index);
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/**
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* Returns {@code true} if this character sequence is empty.
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*
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* @implSpec
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* The default implementation returns the result of calling {@code length() == 0}.
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*
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* @return {@code true} if {@link #length()} is {@code 0}, otherwise
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* {@code false}
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*
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* @since 15
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*/
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default boolean isEmpty() {
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return this.length() == 0;
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}
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/**
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* Returns a {@code CharSequence} that is a subsequence of this sequence.
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* The subsequence starts with the {@code char} value at the specified index and
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@ -684,6 +684,7 @@ public final class String
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*
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* @since 1.6
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*/
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@Override
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public boolean isEmpty() {
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return value.length == 0;
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}
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@ -1645,6 +1645,18 @@ public abstract class $Type$Buffer
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return remaining();
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}
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/**
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* Returns {@code true} if this character buffer is empty.
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*
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* @return {@code true} if there are {@code 0} remaining characters,
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* otherwise {@code false}
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*
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* @since 15
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*/
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public final boolean isEmpty() {
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return remaining() == 0;
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}
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/**
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* Reads the character at the given index relative to the current
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* position.
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104
test/jdk/java/lang/CharSequence/Emptiness.java
Normal file
104
test/jdk/java/lang/CharSequence/Emptiness.java
Normal file
@ -0,0 +1,104 @@
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/*
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* Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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import java.nio.ByteBuffer;
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import java.nio.CharBuffer;
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import org.testng.Assert;
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import org.testng.annotations.Test;
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/**
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* @test
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* @bug 8215401
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* @summary Test to verify the isEmpty method is behaviorally consistent
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* with length
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* @run testng Emptiness
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*/
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public class Emptiness {
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@Test
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public void isEmpty() {
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checkEmpty(new StringBuilder());
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checkEmpty(new StringBuffer());
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checkEmpty("");
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checkEmpty(new CharSequence() {
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@Override public int length() { return 0; }
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@Override public char charAt(int index) { return 'f'; }
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@Override public CharSequence subSequence(int start, int end) {
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throw new UnsupportedOperationException();
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}
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});
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checkEmpty(CharBuffer.wrap(new char[0]));
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checkEmpty(CharBuffer.wrap(""));
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// A CharBuffer being filled is empty when there's no room remaining
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// - or there's nothing in the buffer after a flip
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checkEmpty(ByteBuffer.allocate(0).asCharBuffer());
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checkEmpty(ByteBuffer.allocate(2).asCharBuffer().append('f'));
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checkEmpty(ByteBuffer.allocate(2).asCharBuffer().flip());
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checkEmpty(ByteBuffer.allocateDirect(0).asCharBuffer());
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checkEmpty(ByteBuffer.allocateDirect(2).asCharBuffer().append('f'));
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checkEmpty(ByteBuffer.allocateDirect(2).asCharBuffer().flip());
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}
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@Test
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public void isNotEmpty() {
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checkNotEmpty(new StringBuilder().append("foo"));
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checkNotEmpty(new StringBuffer().append("bar"));
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checkNotEmpty("baz");
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checkNotEmpty(new CharSequence() {
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@Override public int length() { return 1; }
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@Override public char charAt(int index) { return 'f'; }
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@Override public CharSequence subSequence(int start, int end) {
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throw new UnsupportedOperationException();
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}
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});
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checkNotEmpty(CharBuffer.wrap(new char[] { 'f' }));
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checkNotEmpty(CharBuffer.wrap("foo"));
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// A CharBuffer being filled is non-empty when there's room remaining
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// - or when there's something in the buffer after a flip
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checkNotEmpty(ByteBuffer.allocate(2).asCharBuffer());
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checkNotEmpty(ByteBuffer.allocate(4).asCharBuffer().append('f'));
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checkNotEmpty(ByteBuffer.allocate(2).asCharBuffer().append('f').flip());
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checkNotEmpty(ByteBuffer.allocateDirect(2).asCharBuffer());
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checkNotEmpty(ByteBuffer.allocateDirect(4).asCharBuffer().append('f'));
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checkNotEmpty(ByteBuffer.allocateDirect(2).asCharBuffer().append('f').flip());
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}
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public void checkEmpty(CharSequence cs) {
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Assert.assertTrue(cs.isEmpty());
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Assert.assertTrue(consistentWithLength(cs));
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}
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public void checkNotEmpty(CharSequence cs) {
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Assert.assertTrue(!cs.isEmpty());
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Assert.assertTrue(consistentWithLength(cs));
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}
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public boolean consistentWithLength(CharSequence cs) {
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return cs.isEmpty() == (cs.length() == 0);
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}
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}
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