126 lines
4.4 KiB
Java
126 lines
4.4 KiB
Java
/*******************************************************************************
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* This program and the accompanying materials
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* are made available under the terms of the Eclipse Public License v1.0
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* which accompanies this distribution, and is available at
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* http://www.eclipse.org/legal/epl-v10.html.
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*
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* This file is a derivative of code released by the University of
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* California under the terms listed below.
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*
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* Refinement Analysis Tools is Copyright (c) 2007 The Regents of the
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* University of California (Regents). Provided that this notice and
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* the following two paragraphs are included in any distribution of
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* Refinement Analysis Tools or its derivative work, Regents agrees
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* not to assert any of Regents' copyright rights in Refinement
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* Analysis Tools against recipient for recipient's reproduction,
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* preparation of derivative works, public display, public
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* performance, distribution or sublicensing of Refinement Analysis
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* Tools and derivative works, in source code and object code form.
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* This agreement not to assert does not confer, by implication,
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* estoppel, or otherwise any license or rights in any intellectual
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* property of Regents, including, but not limited to, any patents
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* of Regents or Regents' employees.
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*
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* IN NO EVENT SHALL REGENTS BE LIABLE TO ANY PARTY FOR DIRECT,
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* INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES,
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* INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE
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* AND ITS DOCUMENTATION, EVEN IF REGENTS HAS BEEN ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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* REGENTS SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE AND FURTHER DISCLAIMS ANY STATUTORY
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* WARRANTY OF NON-INFRINGEMENT. THE SOFTWARE AND ACCOMPANYING
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* DOCUMENTATION, IF ANY, PROVIDED HEREUNDER IS PROVIDED "AS
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* IS". REGENTS HAS NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT,
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* UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
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*/
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package com.ibm.wala.util;
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import java.util.ArrayList;
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import java.util.Iterator;
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import java.util.List;
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/**
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* Interface for defining an arbitrary predicate on {@link Object}s.
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*/
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public abstract class Predicate<T> {
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public static final Predicate FALSE = new Predicate() {
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@Override
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public boolean test(Object o) {
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return false;
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}
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};
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public static final Predicate TRUE = FALSE.not();
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@SuppressWarnings("unchecked")
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public static <T> Predicate<T> truePred() {
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return TRUE;
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}
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@SuppressWarnings("unchecked")
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public static <T> Predicate<T> falsePred() {
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return FALSE;
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}
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/** Test whether an {@link Object} satisfies this {@link Predicate} */
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public abstract boolean test(T t);
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/** Return a predicate that is a negation of this predicate */
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public Predicate<T> not() {
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final Predicate<T> originalPredicate = this;
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return new Predicate<T>() {
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@Override
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public boolean test(T t) {
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return !originalPredicate.test(t);
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}
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};
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}
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/**
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* Return a predicate that is a conjunction of this predicate and another predicate
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*/
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public Predicate<T> and(final Predicate<T> conjunct) {
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final Predicate<T> originalPredicate = this;
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return new Predicate<T>() {
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@Override
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public boolean test(T t) {
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return originalPredicate.test(t) && conjunct.test(t);
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}
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};
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}
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/**
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* Return a predicate that is a conjunction of this predicate and another predicate
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*/
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public Predicate<T> or(final Predicate<T> disjunct) {
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final Predicate<T> originalPredicate = this;
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return new Predicate<T>() {
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@Override
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public boolean test(T t) {
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return originalPredicate.test(t) || disjunct.test(t);
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}
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};
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}
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/**
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* Filter a collection: generate a new list from an existing collection, consisting of the elements satisfying some predicate.
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*
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* @throws IllegalArgumentException if src == null
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*/
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public static <T> List<T> filter(Iterator<T> src, Predicate<T> pred) throws IllegalArgumentException {
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if (src == null) {
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throw new IllegalArgumentException("src == null");
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}
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ArrayList<T> result = new ArrayList<T>();
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for (; src.hasNext();) {
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T curElem = src.next();
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if (pred.test(curElem))
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result.add(curElem);
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}
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return result;
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}
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}
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