8203442: String::transform
Reviewed-by: smarks, sherman, alanb, darcy, forax, rriggs, scolebourne, dholmes, plevart
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@ -37,6 +37,7 @@ import java.util.Locale;
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import java.util.Objects;
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import java.util.Spliterator;
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import java.util.StringJoiner;
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import java.util.function.Function;
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import java.util.regex.Matcher;
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import java.util.regex.Pattern;
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import java.util.regex.PatternSyntaxException;
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@ -2972,6 +2973,25 @@ public final class String
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return indent(indent > n ? Integer.MIN_VALUE : indent, true);
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}
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/**
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* This method allows the application of a function to {@code this}
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* string. The function should expect a single String argument
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* and produce an {@code R} result.
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*
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* @param f functional interface to a apply
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*
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* @param <R> class of the result
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*
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* @return the result of applying the function to this string
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*
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* @see java.util.function.Function
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*
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* @since 12
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*/
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public <R> R transform(Function<? super String, ? extends R> f) {
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return f.apply(this);
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}
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/**
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* This object (which is already a string!) is itself returned.
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*
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73
test/jdk/java/lang/String/Transform.java
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73
test/jdk/java/lang/String/Transform.java
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@ -0,0 +1,73 @@
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/*
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* Copyright (c) 2018, 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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/*
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* @test
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* @summary Unit tests for String#transform(Function<String, R> f)
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* @run main Transform
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*/
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import java.util.function.Function;
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import java.util.stream.Collectors;
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public class Transform {
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public static void main(String[] args) {
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test1();
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}
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/*
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* Test String#transform(Function<? super String, ? extends R> f) functionality.
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*/
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static void test1() {
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simpleTransform("toUpperCase", "abc", s -> s.toUpperCase());
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simpleTransform("toLowerCase", "ABC", s -> s.toLowerCase());
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simpleTransform("substring", "John Smith", s -> s.substring(0, 4));
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String multiline = " This is line one\n" +
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" This is line two\n" +
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" This is line three\n";
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String expected = "This is line one!\n" +
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" This is line two!\n" +
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" This is line three!\n";
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check("multiline", multiline.transform(string -> {
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return string.lines()
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.map(s -> s.transform(t -> t.substring(4) + "!"))
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.collect(Collectors.joining("\n", "", "\n"));
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}), expected);
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}
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static void simpleTransform(String test, String s, Function<String, String> f) {
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check(test, s.transform(f), f.apply(s));
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}
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static void check(String test, Object output, Object expected) {
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if (output != expected && (output == null || !output.equals(expected))) {
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System.err.println("Testing " + test + ": unexpected result");
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System.err.println("Output:");
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System.err.println(output);
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System.err.println("Expected:");
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System.err.println(expected);
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throw new RuntimeException();
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}
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}
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}
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