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== A binary search implementation. ==



<source lang="java">
/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
*
* Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
*
* The contents of this file are subject to the terms of either the GNU
* General Public License Version 2 only ("GPL") or the Common Development
* and Distribution License("CDDL") (collectively, the "License"). You
* may not use this file except in compliance with the License. You can obtain
* a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
* or glassfish/bootstrap/legal/LICENSE.txt. See the License for the specific
* language governing permissions and limitations under the License.
*
* When distributing the software, include this License Header Notice in each
* file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
* Sun designates this particular file as subject to the "Classpath" exception
* as provided by Sun in the GPL Version 2 section of the License file that
* accompanied this code. If applicable, add the following below the License
* Header, with the fields enclosed by brackets [] replaced by your own
* identifying information: "Portions Copyrighted [year]
* [name of copyright owner]"
*
* Contributor(s):
*
* If you wish your version of this file to be governed by only the CDDL or
* only the GPL Version 2, indicate your decision by adding "[Contributor]
* elects to include this software in this distribution under the [CDDL or GPL
* Version 2] license." If you don"t indicate a single choice of license, a
* recipient has the option to distribute your version of this file under
* either the CDDL, the GPL Version 2 or to extend the choice of license to
* its licensees as provided above. However, if you add GPL Version 2 code
* and therefore, elected the GPL Version 2 license, then the option applies
* only if the new code is made subject to such option by the copyright
* holder.
*/
// ----------------------------------------------------------------------------
/**
* A binary search implementation.
*/
public class BinarySearch {
public int find(final int[] data, final int key) {
int low = 0, high = data.length - 1;
while (low <= high) {
final int i = (low + high) >> 1;
final int v = data[i];
if (v == key)
return i; // this line does not get covered unless there is a match
else if (v < key)
low = i + 1;
else
// v > key
high = i - 1;
}
return -1;
}
}</source>



== Binary Searching ==



<source lang="java">
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
public class MainClass {
public static void main(String args[]) {
String str[] = { "B", "H", "L", "M", "I", "N", "R" };
// Convert to list
List list = new ArrayList(Arrays.asList(str));
// Ensure list sorted
Collections.sort(list);
System.out.println("Sorted list: [length: " + list.size() + "]");
System.out.println(list);
// Search for element in list
int index = Collections.binarySearch(list, "M");
System.out.println("Found M @ " + index);
// Search for element not in list
index = Collections.binarySearch(list, "J");
System.out.println("Didn"t find J @ " + index);
// Insert
int newIndex = -index - 1;
list.add(newIndex, "J");
System.out.println("With J added: [length: " + list.size() + "]");
System.out.println(list);
}
}</source>



<pre class=codeResult>Sorted list: [length: 7]
[B, H, I, L, M, N, R]
Found M @ 4
Didn"t find J @ -4
With J added: [length: 8]
[B, H, I, J, L, M, N, R]</pre>

== Binary search routines ==



<source lang="java">
/*
* Copyright (c) 1998-2002 Carnegie Mellon University. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY CARNEGIE MELLON UNIVERSITY ``AS IS"" AND
* ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY
* NOR ITS EMPLOYEES BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/

/**
* Binary search routines.
*/
public abstract class BinarySearch {

/**
* Search a sorted array of integers.
* @param array Array of integers
* @param offset Starting offset of subarray to search
* @param length Length of subarray to search
* @param x Value to search for
* @return largest index i in subarray (offset <= i <= offset+length)
* such that all elements below i in the subarray are strictly less
* than x. If x is found in the subarray, then array[i] == x (and i is
* the first occurence of x in the subarray). If x is not found,
* then array[i] is where x should be inserted in the sort order.
*/
public static int search (int[] array, int offset, int length, int x) {
// handle 0-length subarray case right away
if (length <= 0)
return offset;
int low = offset;
int high = offset+length-1;
// since length > 0, array[low] and array[high] are valid indices
if (x <= array[low])
return low;
if (x > array[high])
return high+1;

while (low+1 < high) {
// loop invariant: array[low] < x <= array[high],
// offset <= low < high < offset+length
int mid = (low + high)/2;
if (x <= array[mid])
high = mid;
else
low = mid;
}
// now we have array[low] < x <= array[high]
// && (low+1 == high || low == high)
// implies low+1 == high
//debug.assertion (low+1 == high);
return high;
}
}</source>



== Check whether the given Collection contains the given element instance. ==



<source lang="java">
import java.util.Arrays;
import java.util.Collection;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Properties;
/*
* Copyright 2002-2007 the original author or authors.
*
* Licensed 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.
*/

/**
* Miscellaneous collection utility methods.
* Mainly for internal use within the framework.
*
* @author Juergen Hoeller
* @author Rob Harrop
* @since 1.1.3
*/
abstract class CollectionUtils {

/**
* Check whether the given Collection contains the given element instance.
* Enforces the given instance to be present, rather than returning
* <code>true</code> for an equal element as well.
* @param collection the Collection to check
* @param element the element to look for
* @return <code>true</code> if found, <code>false</code> else
*/
public static boolean containsInstance(Collection collection, Object element) {
if (collection != null) {
for (Iterator it = collection.iterator(); it.hasNext();) {
Object candidate = it.next();
if (candidate == element) {
return true;
}
}
}
return false;
}
/**
* Return <code>true</code> if the supplied Collection is <code>null</code>
* or empty. Otherwise, return <code>false</code>.
* @param collection the Collection to check
* @return whether the given Collection is empty
*/
public static boolean isEmpty(Collection collection) {
return (collection == null || collection.isEmpty());
}
/**
* Return <code>true</code> if the supplied Map is <code>null</code>
* or empty. Otherwise, return <code>false</code>.
* @param map the Map to check
* @return whether the given Map is empty
*/
public static boolean isEmpty(Map map) {
return (map == null || map.isEmpty());
}

/**
* Return <code>true</code> if any element in "<code>candidates</code>" is
* contained in "<code>source</code>"; otherwise returns <code>false</code>.
* @param source the source Collection
* @param candidates the candidates to search for
* @return whether any of the candidates has been found
*/
public static boolean containsAny(Collection source, Collection candidates) {
if (isEmpty(source) || isEmpty(candidates)) {
return false;
}
for (Iterator it = candidates.iterator(); it.hasNext();) {
if (source.contains(it.next())) {
return true;
}
}
return false;
}
/**
* Return the first element in "<code>candidates</code>" that is contained in
* "<code>source</code>". If no element in "<code>candidates</code>" is present in
* "<code>source</code>" returns <code>null</code>. Iteration order is
* {@link Collection} implementation specific.
* @param source the source Collection
* @param candidates the candidates to search for
* @return the first present object, or <code>null</code> if not found
*/
public static Object findFirstMatch(Collection source, Collection candidates) {
if (isEmpty(source) || isEmpty(candidates)) {
return null;
}
for (Iterator it = candidates.iterator(); it.hasNext();) {
Object candidate = it.next();
if (source.contains(candidate)) {
return candidate;
}
}
return null;
}
/**
* Find a value of the given type in the given Collection.
* @param collection the Collection to search
* @param type the type to look for
* @return a value of the given type found, or <code>null</code> if none
* @throws IllegalArgumentException if more than one value of the given type found
*/
public static Object findValueOfType(Collection collection, Class type) throws IllegalArgumentException {
if (isEmpty(collection)) {
return null;
}
Class typeToUse = (type != null ? type : Object.class);
Object value = null;
for (Iterator it = collection.iterator(); it.hasNext();) {
Object obj = it.next();
if (typeToUse.isInstance(obj)) {
if (value != null) {
throw new IllegalArgumentException("More than one value of type [" + typeToUse.getName() + "] found");
}
value = obj;
}
}
return value;
}
/**
* Determine whether the given Collection only contains a single unique object.
* @param collection the Collection to check
* @return <code>true</code> if the collection contains a single reference or
* multiple references to the same instance, <code>false</code> else
*/
public static boolean hasUniqueObject(Collection collection) {
if (isEmpty(collection)) {
return false;
}
boolean hasCandidate = false;
Object candidate = null;
for (Iterator it = collection.iterator(); it.hasNext();) {
Object elem = it.next();
if (!hasCandidate) {
hasCandidate = true;
candidate = elem;
}
else if (candidate != elem) {
return false;
}
}
return true;
}
}</source>



== Find a value of the given type in the given Collection ==



<source lang="java">
import java.util.Arrays;
import java.util.Collection;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Properties;
/*
* Copyright 2002-2007 the original author or authors.
*
* Licensed 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.
*/

/**
* Miscellaneous collection utility methods.
* Mainly for internal use within the framework.
*
* @author Juergen Hoeller
* @author Rob Harrop
* @since 1.1.3
*/
abstract class CollectionUtils {

/**
* Find a value of the given type in the given Collection.
* @param collection the Collection to search
* @param type the type to look for
* @return a value of the given type found, or <code>null</code> if none
* @throws IllegalArgumentException if more than one value of the given type found
*/
public static Object findValueOfType(Collection collection, Class type) throws IllegalArgumentException {
if (isEmpty(collection)) {
return null;
}
Class typeToUse = (type != null ? type : Object.class);
Object value = null;
for (Iterator it = collection.iterator(); it.hasNext();) {
Object obj = it.next();
if (typeToUse.isInstance(obj)) {
if (value != null) {
throw new IllegalArgumentException("More than one value of type [" + typeToUse.getName() + "] found");
}
value = obj;
}
}
return value;
}
/**
* Return <code>true</code> if the supplied Collection is <code>null</code>
* or empty. Otherwise, return <code>false</code>.
* @param collection the Collection to check
* @return whether the given Collection is empty
*/
public static boolean isEmpty(Collection collection) {
return (collection == null || collection.isEmpty());
}
/**
* Return <code>true</code> if the supplied Map is <code>null</code>
* or empty. Otherwise, return <code>false</code>.
* @param map the Map to check
* @return whether the given Map is empty
*/
public static boolean isEmpty(Map map) {
return (map == null || map.isEmpty());
}

/**
* Return the first element in "<code>candidates</code>" that is contained in
* "<code>source</code>". If no element in "<code>candidates</code>" is present in
* "<code>source</code>" returns <code>null</code>. Iteration order is
* {@link Collection} implementation specific.
* @param source the source Collection
* @param candidates the candidates to search for
* @return the first present object, or <code>null</code> if not found
*/
public static Object findFirstMatch(Collection source, Collection candidates) {
if (isEmpty(source) || isEmpty(candidates)) {
return null;
}
for (Iterator it = candidates.iterator(); it.hasNext();) {
Object candidate = it.next();
if (source.contains(candidate)) {
return candidate;
}
}
return null;
}

/**
* Determine whether the given Collection only contains a single unique object.
* @param collection the Collection to check
* @return <code>true</code> if the collection contains a single reference or
* multiple references to the same instance, <code>false</code> else
*/
public static boolean hasUniqueObject(Collection collection) {
if (isEmpty(collection)) {
return false;
}
boolean hasCandidate = false;
Object candidate = null;
for (Iterator it = collection.iterator(); it.hasNext();) {
Object elem = it.next();
if (!hasCandidate) {
hasCandidate = true;
candidate = elem;
}
else if (candidate != elem) {
return false;
}
}
return true;
}
}</source>



== Get the difference of two collections ==



<source lang="java">
import java.util.ArrayList;
import java.util.Collection;

public class Utils {
public static <T> Collection<T> diff(Collection<T> c1, Collection<T> c2) {
if (c1 == null || c1.size() == 0 || c2 == null || c2.size() == 0) {
return c1;
}
Collection<T> difference = new ArrayList<T>();
for (T item : c1) {
if (!c2.contains(item)) {
difference.add(item);
}
}
return difference;
}

}</source>



== Return the first element in "candidates" that is contained in source ==



<source lang="java">
import java.util.Arrays;
import java.util.Collection;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Properties;
/*
* Copyright 2002-2007 the original author or authors.
*
* Licensed 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.
*/

/**
* Miscellaneous collection utility methods.
* Mainly for internal use within the framework.
*
* @author Juergen Hoeller
* @author Rob Harrop
* @since 1.1.3
*/
abstract class CollectionUtils {

/**
* Return the first element in "<code>candidates</code>" that is contained in
* "<code>source</code>". If no element in "<code>candidates</code>" is present in
* "<code>source</code>" returns <code>null</code>. Iteration order is
* {@link Collection} implementation specific.
* @param source the source Collection
* @param candidates the candidates to search for
* @return the first present object, or <code>null</code> if not found
*/
public static Object findFirstMatch(Collection source, Collection candidates) {
if (isEmpty(source) || isEmpty(candidates)) {
return null;
}
for (Iterator it = candidates.iterator(); it.hasNext();) {
Object candidate = it.next();
if (source.contains(candidate)) {
return candidate;
}
}
return null;
}
/**
* Return <code>true</code> if the supplied Collection is <code>null</code>
* or empty. Otherwise, return <code>false</code>.
* @param collection the Collection to check
* @return whether the given Collection is empty
*/
public static boolean isEmpty(Collection collection) {
return (collection == null || collection.isEmpty());
}
/**
* Return <code>true</code> if the supplied Map is <code>null</code>
* or empty. Otherwise, return <code>false</code>.
* @param map the Map to check
* @return whether the given Map is empty
*/
public static boolean isEmpty(Map map) {
return (map == null || map.isEmpty());
}
}</source>

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Admin: 1 версия

в 17:44, 31 мая 2010