8203442: String::transform

Reviewed-by: smarks, sherman, alanb, darcy, forax, rriggs, scolebourne, dholmes, plevart
This commit is contained in:
Jim Laskey 2018-11-26 12:20:06 -04:00
parent 6d25f18bad
commit 40d4ff864c
2 changed files with 93 additions and 0 deletions
src/java.base/share/classes/java/lang
test/jdk/java/lang/String

@ -37,6 +37,7 @@ import java.util.Locale;
import java.util.Objects;
import java.util.Spliterator;
import java.util.StringJoiner;
import java.util.function.Function;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;
@ -2972,6 +2973,25 @@ public final class String
return indent(indent > n ? Integer.MIN_VALUE : indent, true);
}
/**
* This method allows the application of a function to {@code this}
* string. The function should expect a single String argument
* and produce an {@code R} result.
*
* @param f functional interface to a apply
*
* @param <R> class of the result
*
* @return the result of applying the function to this string
*
* @see java.util.function.Function
*
* @since 12
*/
public <R> R transform(Function<? super String, ? extends R> f) {
return f.apply(this);
}
/**
* This object (which is already a string!) is itself returned.
*

@ -0,0 +1,73 @@
/*
* Copyright (c) 2018, 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
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/*
* @test
* @summary Unit tests for String#transform(Function<String, R> f)
* @run main Transform
*/
import java.util.function.Function;
import java.util.stream.Collectors;
public class Transform {
public static void main(String[] args) {
test1();
}
/*
* Test String#transform(Function<? super String, ? extends R> f) functionality.
*/
static void test1() {
simpleTransform("toUpperCase", "abc", s -> s.toUpperCase());
simpleTransform("toLowerCase", "ABC", s -> s.toLowerCase());
simpleTransform("substring", "John Smith", s -> s.substring(0, 4));
String multiline = " This is line one\n" +
" This is line two\n" +
" This is line three\n";
String expected = "This is line one!\n" +
" This is line two!\n" +
" This is line three!\n";
check("multiline", multiline.transform(string -> {
return string.lines()
.map(s -> s.transform(t -> t.substring(4) + "!"))
.collect(Collectors.joining("\n", "", "\n"));
}), expected);
}
static void simpleTransform(String test, String s, Function<String, String> f) {
check(test, s.transform(f), f.apply(s));
}
static void check(String test, Object output, Object expected) {
if (output != expected && (output == null || !output.equals(expected))) {
System.err.println("Testing " + test + ": unexpected result");
System.err.println("Output:");
System.err.println(output);
System.err.println("Expected:");
System.err.println(expected);
throw new RuntimeException();
}
}
}