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[COLLECTIONS-550] Added IterableUtils#toString(...) to newly created IterableUtils class. Thanks to Goncalo Marques. This closes #7. 

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/collections/trunk@1656600 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Thomas Neidhart 2015-02-02 23:10:32 +00:00
parent 2db7aa771a
commit 39513f9142
4 changed files with 330 additions and 0 deletions
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3
pom.xml
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@ -429,6 +429,9 @@
<contributor>
<name>Geoff Schoeman</name>
</contributor>
<contributor>
<name>Goncalo Marques</name>
</contributor>
</contributors>
<dependencies>

4
src/changes/changes.xml
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@ -22,6 +22,10 @@
<body>
<release version="4.1" date="TBD" description="">
<action issue="COLLECTIONS-427" dev="tn" type="add" due-to="Gonçalo Marques">
Added "toString(...)" methods to newly created "IteratorUtils" class to get a
string representation of an Iterable instance similar to "Arrays#toString(...)".
</action>
<action issue="COLLECTIONS-427" dev="tn" type="fix">
Reverted performance improvement for "SetUniqueList#retainAll(Collection)"
introduced in 4.0. Added clarifying javadoc wrt runtime complexity instead.

128
src/main/java/org/apache/commons/collections4/IterableUtils.java Normal file
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@ -0,0 +1,128 @@
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.collections4;
/**
* Provides utility methods and decorators for {@link Iterable} instances.
*
* @since 4.1
* @version $Id$
*/
public class IterableUtils {
/**
* Default prefix used while converting an Iterable to its String representation.
*/
private static final String DEFAULT_TOSTRING_PREFIX = "[";
/**
* Default suffix used while converting an Iterable to its String representation.
*/
private static final String DEFAULT_TOSTRING_SUFFIX = "]";
/**
* Default delimiter used to delimit elements while converting an Iterable
* to its String representation.
*/
private static final String DEFAULT_TOSTRING_DELIMITER = ", ";
/**
* Returns a string representation of the elements of the specified iterable.
* The string representation consists of a list of the iterable's elements,
* enclosed in square brackets ({@code "[]"}). Adjacent elements are separated
* by the characters {@code ", "} (a comma followed by a space). Elements are
* converted to strings as by {@code String.valueOf(Object)}.
*
* @param <C> the element type
* @param iterable the iterable to convert to a string
* @return a string representation of {@code iterable}
* @throws IllegalArgumentException if {@code iterable} is null
*/
public static <C> String toString(Iterable<C> iterable) {
return toString(iterable, new Transformer<C, String>() {
public String transform(C input) {
return String.valueOf(input);
}
}, DEFAULT_TOSTRING_DELIMITER, DEFAULT_TOSTRING_PREFIX, DEFAULT_TOSTRING_SUFFIX);
}
/**
* Returns a string representation of the elements of the specified iterable.
* The string representation consists of a list of the iterable's elements,
* enclosed in square brackets ({@code "[]"}). Adjacent elements are separated
* by the characters {@code ", "} (a comma followed by a space). Elements are
* converted to strings as by using the provided {@code transformer}.
*
* @param <C> the element type
* @param iterable the iterable to convert to a string
* @param transformer the transformer used to get a string representation of an element
* @return a string representation of {@code iterable}
* @throws IllegalArgumentException if {@code iterable} or {@code transformer} is null
*/
public static <C> String toString(Iterable<C> iterable, Transformer<? super C, String> transformer) {
return toString(iterable, transformer, DEFAULT_TOSTRING_DELIMITER,
DEFAULT_TOSTRING_PREFIX, DEFAULT_TOSTRING_SUFFIX);
}
/**
* Returns a string representation of the elements of the specified iterable.
* The string representation consists of a list of the iterable's elements,
* enclosed by the provided {@code prefix} and {@code suffix}. Adjacent elements
* are separated by the provided {@code delimiter}. Elements are converted to
* strings as by using the provided {@code transformer}.
*
* @param <C> the element type
* @param iterable the iterable to convert to a string
* @param transformer the transformer used to get a string representation of an element
* @param delimiter the string to delimit elements
* @param prefix the prefix, prepended to the string representation
* @param suffix the suffix, appended to the string representation
* @return a string representation of {@code iterable}
* @throws IllegalArgumentException if any argument is null
*/
public static <C> String toString(Iterable<C> iterable,
Transformer<? super C, String> transformer,
String delimiter,
String prefix,
String suffix) {
if (iterable == null) {
throw new IllegalArgumentException("iterable may not be null");
}
if (transformer == null) {
throw new IllegalArgumentException("transformer may not be null");
}
if (delimiter == null) {
throw new IllegalArgumentException("delimiter may not be null");
}
if (prefix == null) {
throw new IllegalArgumentException("prefix may not be null");
}
if (suffix == null) {
throw new IllegalArgumentException("suffix may not be null");
}
final StringBuilder stringBuilder = new StringBuilder(prefix);
for(final C element : iterable) {
stringBuilder.append(transformer.transform(element));
stringBuilder.append(delimiter);
}
if(stringBuilder.length() > prefix.length()) {
stringBuilder.setLength(stringBuilder.length() - delimiter.length());
}
stringBuilder.append(suffix);
return stringBuilder.toString();
}
}

195
src/test/java/org/apache/commons/collections4/IterableUtilsTest.java Normal file
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.collections4;
import java.util.ArrayList;
import java.util.List;
import junit.framework.Test;
/**
* Tests for IterableUtils.
*
* @since 4.1
* @version $Id$
*/
public class IterableUtilsTest extends BulkTest {
/**
* Iterable of {@link Integer}s
*/
private Iterable<Integer> iterableA = null;
public IterableUtilsTest(final String name) {
super(name);
}
public static Test suite() {
return BulkTest.makeSuite(IterableUtilsTest.class);
}
@Override
public void setUp() {
List<Integer> listA = new ArrayList<Integer>();
listA.add(1);
listA.add(2);
listA.add(2);
listA.add(3);
listA.add(3);
listA.add(3);
listA.add(4);
listA.add(4);
listA.add(4);
listA.add(4);
iterableA = listA;
}
public void testToString() {
String result = IterableUtils.toString(iterableA);
assertEquals("[1, 2, 2, 3, 3, 3, 4, 4, 4, 4]", result);
result = IterableUtils.toString(new ArrayList<Integer>());
assertEquals("[]", result);
try {
IterableUtils.toString(null);
fail("expecting IllegalArgumentException");
} catch (final IllegalArgumentException iae) {
// expected
}
result = IterableUtils.toString(iterableA, new Transformer<Integer, String>() {
public String transform(Integer input) {
return new Integer(input * 2).toString();
}
});
assertEquals("[2, 4, 4, 6, 6, 6, 8, 8, 8, 8]", result);
result = IterableUtils.toString(new ArrayList<Integer>(), new Transformer<Integer, String>() {
public String transform(Integer input) {
fail("not supposed to reach here");
return "";
}
});
assertEquals("[]", result);
try {
IterableUtils.toString(null, new Transformer<Integer, String>() {
public String transform(Integer input) {
fail("not supposed to reach here");
return "";
}
});
fail("expecting IllegalArgumentException");
} catch (final IllegalArgumentException iae) {
// expected
}
}
public void testToStringDelimiter() {
Transformer<Integer, String> transformer = new Transformer<Integer, String>() {
public String transform(Integer input) {
return new Integer(input * 2).toString();
}
};
String result = IterableUtils.toString(iterableA, transformer, "", "", "");
assertEquals("2446668888", result);
result = IterableUtils.toString(iterableA, transformer, ",", "", "");
assertEquals("2,4,4,6,6,6,8,8,8,8", result);
result = IterableUtils.toString(iterableA, transformer, "", "[", "]");
assertEquals("[2446668888]", result);
result = IterableUtils.toString(iterableA, transformer, ",", "[", "]");
assertEquals("[2,4,4,6,6,6,8,8,8,8]", result);
result = IterableUtils.toString(iterableA, transformer, ",", "[[", "]]");
assertEquals("[[2,4,4,6,6,6,8,8,8,8]]", result);
result = IterableUtils.toString(iterableA, transformer, ",,", "[", "]");
assertEquals("[2,,4,,4,,6,,6,,6,,8,,8,,8,,8]", result);
result = IterableUtils.toString(iterableA, transformer, ",,", "((", "))");
assertEquals("((2,,4,,4,,6,,6,,6,,8,,8,,8,,8))", result);
result = IterableUtils.toString(new ArrayList<Integer>(), transformer, "", "(", ")");
assertEquals("()", result);
result = IterableUtils.toString(new ArrayList<Integer>(), transformer, "", "", "");
assertEquals("", result);
}
public void testToStringWithNullArguments() {
try {
IterableUtils.toString(null, new Transformer<Integer, String>() {
public String transform(Integer input) {
fail("not supposed to reach here");
return "";
}
}, "", "(", ")");
fail("expecting IllegalArgumentException");
} catch (final IllegalArgumentException iae) {
// expected
}
try {
IterableUtils.toString(new ArrayList<Integer>(), null, "", "(", ")");
fail("expecting IllegalArgumentException");
} catch (final IllegalArgumentException iae) {
// expected
}
try {
IterableUtils.toString(new ArrayList<Integer>(), new Transformer<Integer, String>() {
public String transform(Integer input) {
fail("not supposed to reach here");
return "";
}
}, null, "(", ")");
fail("expecting IllegalArgumentException");
} catch (final IllegalArgumentException iae) {
// expected
}
try {
IterableUtils.toString(new ArrayList<Integer>(), new Transformer<Integer, String>() {
public String transform(Integer input) {
fail("not supposed to reach here");
return "";
}
}, "", null, ")");
fail("expecting IllegalArgumentException");
} catch (final IllegalArgumentException iae) {
// expected
}
try {
IterableUtils.toString(new ArrayList<Integer>(), new Transformer<Integer, String>() {
public String transform(Integer input) {
fail("not supposed to reach here");
return "";
}
}, "", "(", null);
fail("expecting IllegalArgumentException");
} catch (final IllegalArgumentException iae) {
// expected
}
}
}