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feat: Java 代码性能提升技巧(https://www.wdbyte.com/java/code-5-tips.html)
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‎core-java-modules/core-java-performance-code/README.md‎

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## core-java-performance-code
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当前模块包含代码性能相关代码
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### 相关文章
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- [Java 中的 5 个代码性能提升技巧](https://www.wdbyte.com/java/code-5-tips.html)

‎core-java-modules/core-java-performance-code/pom.xml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<parent>
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<artifactId>core-java-modules</artifactId>
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<groupId>com.wdbyte.core-java-modules</groupId>
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<version>1.0.0-SNAPSHOT</version>
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</parent>
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<modelVersion>4.0.0</modelVersion>
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<artifactId>core-java-performance-code</artifactId>
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<version>1.0.0-SNAPSHOT</version>
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<packaging>jar</packaging>
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<properties>
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<maven.compiler.source>1.8</maven.compiler.source>
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<maven.compiler.target>1.8</maven.compiler.target>
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</properties>
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<dependencies>
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<!-- https://mvnrepository.com/artifact/org.openjdk.jmh/jmh-core -->
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<dependency>
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<groupId>org.openjdk.jmh</groupId>
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<artifactId>jmh-core</artifactId>
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<version>1.33</version>
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</dependency>
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<dependency>
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<groupId>org.openjdk.jmh</groupId>
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<artifactId>jmh-generator-annprocess</artifactId>
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<version>1.33</version>
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<scope>provided</scope>
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</dependency>
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</dependencies>
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</project>

‎core-java-modules/core-java-performance-code/src/main/java/com/wdbyte/EnumIteration.java‎

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package com.wdbyte;
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import java.util.EnumSet;
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import org.openjdk.jmh.annotations.Benchmark;
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import org.openjdk.jmh.annotations.Measurement;
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import org.openjdk.jmh.annotations.Scope;
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import org.openjdk.jmh.annotations.State;
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import org.openjdk.jmh.annotations.Warmup;
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import org.openjdk.jmh.infra.Blackhole;
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/**
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* 枚举类遍历测试
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*
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* @author https://www.wdbyte.com
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* @date 2021/12/07
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*/
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@State(Scope.Benchmark)
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@Warmup(iterations = 3, time = 3)
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@Measurement(iterations = 5, time = 3)
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public class EnumIteration {
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enum FourteenEnum {
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a, b, c, d, e, f, g,
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h, i, j, k, l, m, n,
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o, p, q, r, s, t,
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u, v, w, x, y, z;
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static final FourteenEnum[] VALUES;
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static {
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VALUES = values();
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}
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}
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@Benchmark
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public void valuesEnum(Blackhole bh) {
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for (FourteenEnum value : FourteenEnum.values()) {
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bh.consume(value.ordinal());
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}
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}
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@Benchmark
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public void enumSetEnum(Blackhole bh) {
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for (FourteenEnum value : EnumSet.allOf(FourteenEnum.class)) {
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bh.consume(value.ordinal());
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}
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}
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@Benchmark
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public void cacheEnums(Blackhole bh) {
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for (FourteenEnum value : FourteenEnum.VALUES) {
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bh.consume(value.ordinal());
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}
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}
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}
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‎core-java-modules/core-java-performance-code/src/main/java/com/wdbyte/EnumMapBenchmark.java‎

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package com.wdbyte;
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import java.util.EnumMap;
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import java.util.HashMap;
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import java.util.SplittableRandom;
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import java.util.UUID;
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import org.openjdk.jmh.annotations.Benchmark;
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import org.openjdk.jmh.annotations.Level;
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import org.openjdk.jmh.annotations.Measurement;
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import org.openjdk.jmh.annotations.Scope;
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import org.openjdk.jmh.annotations.Setup;
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import org.openjdk.jmh.annotations.State;
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import org.openjdk.jmh.annotations.Warmup;
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import org.openjdk.jmh.infra.Blackhole;
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@State(Scope.Benchmark)
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@Warmup(iterations = 3, time = 3)
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@Measurement(iterations = 5, time = 3)
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public class EnumMapBenchmark {
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enum AnEnum {
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a, b, c, d, e, f, g,
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h, i, j, k, l, m, n,
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o, p, q, r, s, t,
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u, v, w, x, y, z;
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}
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/** 要查找的 key 的数量 */
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private static int size = 10000;
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/** 随机数种子 */
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private static int seed = 99;
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@State(Scope.Benchmark)
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public static class EnumMapState {
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private EnumMap<AnEnum, String> map;
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private AnEnum[] values;
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@Setup(Level.Trial)
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public void setup() {
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map = new EnumMap<>(AnEnum.class);
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values = new AnEnum[size];
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AnEnum[] enumValues = AnEnum.values();
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SplittableRandom random = new SplittableRandom(seed);
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for (int i = 0; i < size; i++) {
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int nextInt = random.nextInt(0, Integer.MAX_VALUE);
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values[i] = enumValues[nextInt % enumValues.length];
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}
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for (AnEnum value : enumValues) {
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map.put(value, UUID.randomUUID().toString());
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}
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}
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}
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@State(Scope.Benchmark)
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public static class HashMapState{
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private HashMap<String, String> map;
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private String[] values;
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@Setup(Level.Trial)
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public void setup() {
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map = new HashMap<>();
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values = new String[size];
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AnEnum[] enumValues = AnEnum.values();
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int pos = 0;
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SplittableRandom random = new SplittableRandom(seed);
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for (int i = 0; i < size; i++) {
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int nextInt = random.nextInt(0, Integer.MAX_VALUE);
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values[i] = enumValues[nextInt % enumValues.length].toString();
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}
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for (AnEnum value : enumValues) {
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map.put(value.toString(), UUID.randomUUID().toString());
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}
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}
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}
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@Benchmark
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public void enumMap(EnumMapState state, Blackhole bh) {
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for (AnEnum value : state.values) {
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bh.consume(state.map.get(value));
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}
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}
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@Benchmark
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public void hashMap(HashMapState state, Blackhole bh) {
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for (String value : state.values) {
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bh.consume(state.map.get(value));
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}
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}
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}
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‎core-java-modules/core-java-performance-code/src/main/java/com/wdbyte/HashMapKey.java‎

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package com.wdbyte;
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import java.util.HashMap;
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import java.util.Map;
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import java.util.UUID;
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import org.apache.commons.lang3.tuple.MutablePair;
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import org.apache.commons.lang3.tuple.Pair;
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import org.openjdk.jmh.annotations.Benchmark;
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import org.openjdk.jmh.annotations.Level;
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import org.openjdk.jmh.annotations.Measurement;
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import org.openjdk.jmh.annotations.OperationsPerInvocation;
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import org.openjdk.jmh.annotations.Scope;
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import org.openjdk.jmh.annotations.Setup;
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import org.openjdk.jmh.annotations.State;
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import org.openjdk.jmh.annotations.Warmup;
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import org.openjdk.jmh.infra.Blackhole;
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/**
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* @author https://www.wdbyte.com
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* @date 2021/12/06
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*/
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@State(Scope.Benchmark)
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@Warmup(iterations = 3, time = 3)
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@Measurement(iterations = 5, time = 3)
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public class HashMapKey {
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private int size = 1024;
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private Map<String, Object> stringMap;
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private Map<Pair, Object> pairMap;
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private String[] prefixes;
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private String[] suffixes;
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@Setup(Level.Trial)
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public void setup() {
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prefixes = new String[size];
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suffixes = new String[size];
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stringMap = new HashMap<>();
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pairMap = new HashMap<>();
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for (int i = 0; i < size; ++i) {
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prefixes[i] = UUID.randomUUID().toString();
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suffixes[i] = UUID.randomUUID().toString();
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stringMap.put(prefixes[i] + ";" + suffixes[i], i);
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// use new String to avoid reference equality speeding up the equals calls
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pairMap.put(new MutablePair(prefixes[i], suffixes[i]), i);
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}
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}
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@Benchmark
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@OperationsPerInvocation(1024)
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public void stringKey(Blackhole bh) {
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for (int i = 0; i < prefixes.length; i++) {
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bh.consume(stringMap.get(prefixes[i] + ";" + suffixes[i]));
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}
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}
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@Benchmark
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@OperationsPerInvocation(1024)
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public void pairMap(Blackhole bh) {
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for (int i = 0; i < prefixes.length; i++) {
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bh.consume(pairMap.get(new MutablePair(prefixes[i], suffixes[i])));
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}
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}
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}

‎core-java-modules/core-java-performance-code/src/main/java/com/wdbyte/HashMapSize.java‎

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package com.wdbyte;
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import java.util.HashMap;
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import org.openjdk.jmh.annotations.Benchmark;
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import org.openjdk.jmh.annotations.Measurement;
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import org.openjdk.jmh.annotations.Param;
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import org.openjdk.jmh.annotations.Scope;
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import org.openjdk.jmh.annotations.State;
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import org.openjdk.jmh.annotations.Warmup;
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/**
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* @author https://www.wdbyte.com
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* @date 2021/12/06
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*/
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@State(Scope.Benchmark)
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@Warmup(iterations = 3,time = 3)
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@Measurement(iterations = 5,time = 3)
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public class HashMapSize {
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@Param({"14"})
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int keys;
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@Param({"16", "32"})
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int size;
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@Benchmark
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public HashMap<Integer, Integer> getHashMap() {
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HashMap<Integer, Integer> map = new HashMap<>(size);
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for (int i = 0; i < keys; i++) {
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map.put(i, i);
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}
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return map;
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}
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}

‎core-java-modules/core-java-performance-code/src/main/java/com/wdbyte/StringInJdk.java‎

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package com.wdbyte;
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import java.nio.charset.StandardCharsets;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.UUID;
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import org.openjdk.jmh.annotations.Benchmark;
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import org.openjdk.jmh.annotations.Level;
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import org.openjdk.jmh.annotations.Measurement;
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import org.openjdk.jmh.annotations.Param;
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import org.openjdk.jmh.annotations.Scope;
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import org.openjdk.jmh.annotations.Setup;
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import org.openjdk.jmh.annotations.State;
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import org.openjdk.jmh.annotations.Warmup;
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import org.openjdk.jmh.infra.Blackhole;
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/**
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* @author niulang
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* @date 2021/12/23
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*/
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@State(Scope.Benchmark)
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@Warmup(iterations = 3, time = 3)
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@Measurement(iterations = 5, time = 3)
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public class StringInJdk {
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@Param({"10000"})
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private int size;
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private String[] stringArray;
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private List<byte[]> byteList;
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@Setup(Level.Trial)
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public void setup() {
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byteList = new ArrayList<>(size);
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stringArray = new String[size];
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for (int i = 0; i < size; i++) {
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String uuid = UUID.randomUUID().toString();
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stringArray[i] = uuid;
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byteList.add(uuid.getBytes(StandardCharsets.UTF_8));
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}
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}
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@Benchmark
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public void byteToString(Blackhole bh) {
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for (byte[] bytes : byteList) {
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bh.consume(new String(bytes, StandardCharsets.UTF_8));
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}
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}
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@Benchmark
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public void stringToByte(Blackhole bh) {
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for (String s : stringArray) {
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bh.consume(s.getBytes(StandardCharsets.UTF_8));
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}
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}
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}

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