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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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package org.apache.lucene.util;
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import java.util.Random;
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public class TestStringIntern extends LuceneTestCase {
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String[] internedStrings;
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private String randStr(int len) {
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char[] arr = new char[len];
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for (int i=0; i<len; i++) {
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arr[i] = (char)('a' + random.nextInt(26));
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return new String(arr);
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private void makeStrings(int sz) {
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testStrings = new String[sz];
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internedStrings = new String[sz];
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for (int i=0; i<sz; i++) {
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testStrings[i] = randStr(random.nextInt(8)+3);
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public void testStringIntern() throws InterruptedException {
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makeStrings(1024*10); // something greater than the capacity of the default cache size
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// makeStrings(100); // realistic for perf testing
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// final int iter=100000;
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final int iter = atLeast(100000);
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// StringHelper.interner = new StringInterner();
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Thread[] threads = new Thread[nThreads];
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for (int i=0; i<nThreads; i++) {
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threads[i] = new Thread() {
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Random rand = new Random(seed);
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String[] myInterned = new String[testStrings.length];
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for (int j=0; j<iter; j++) {
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int idx = rand.nextInt(testStrings.length);
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String s = testStrings[idx];
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if (rand.nextBoolean()) s = new String(s); // make a copy half of the time
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String interned = StringHelper.intern(s);
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String prevInterned = myInterned[idx];
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String otherInterned = internedStrings[idx];
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// test against other threads
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if (otherInterned != null && otherInterned != interned) {
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internedStrings[idx] = interned;
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// test against local copy
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if (prevInterned != null && prevInterned != interned) {
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myInterned[idx] = interned;
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for (int i=0; i<nThreads; i++) {