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Add stage 1 lesson 2
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‎.gitignore

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.DS_Store
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target
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*.class
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.settings
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.classpath
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# maven ignore
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target/
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*.jar
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!.mvn/wrapper/*
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*.war
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*.zip
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*.tar
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*.tar.gz
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# eclipse ignore
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.settings/
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.project
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.mvn
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.idea
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.classpath
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# idea ignore
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.idea/
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*.ipr
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*.iml
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*.iws
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# temp ignore
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*.log
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*.cache
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*.diff
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*.patch
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*.tmp
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# system ignore
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.DS_Store
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Thumbs.db
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*.orig

‎「一入 Java 深似海 」/代码/segmentfault/deep-in-java/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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<modelVersion>4.0.0</modelVersion>
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<groupId>com.segmentfault</groupId>
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<artifactId>deep-in-java</artifactId>
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<version>1.0-SNAPSHOT</version>
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<packaging>pom</packaging>
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<name>「一入 Java 深似海 」系列</name>
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<modules>
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<module>stage-1</module>
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</modules>
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</project>

‎「一入 Java 深似海 」/代码/segmentfault/deep-in-java/stage-1/lesson-2/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>stage-1</artifactId>
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<groupId>com.segmentfault</groupId>
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<version>1.0-SNAPSHOT</version>
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</parent>
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<modelVersion>4.0.0</modelVersion>
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<name>「一入 Java 深似海 」系列 :: 第一期 :: 第二节</name>
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<build>
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<plugins>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-compiler-plugin</artifactId>
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<configuration>
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<source>8</source>
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<target>8</target>
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</configuration>
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</plugin>
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</plugins>
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</build>
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<artifactId>stage-1-lesson-2</artifactId>
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</project>

‎「一入 Java 深似海 」/代码/segmentfault/deep-in-java/stage-1/lesson-2/src/main/java/com/segmentfault/deep/in/java/ClassName.java

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package com.segmentfault.deep.in.java;
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class ClassName {
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public static void main(String[] args) {
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}
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}

‎「一入 Java 深似海 」/代码/segmentfault/deep-in-java/stage-1/lesson-2/src/main/java/com/segmentfault/deep/in/java/CloneableDemo.java

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package com.segmentfault.deep.in.java;
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public class CloneableDemo {
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public static void main(String[] args) throws CloneNotSupportedException {
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String desc = "Hello,World";
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Data data = new Data();
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data.setValue(1);
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data.setDesc(desc);
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Data copy = data.clone();
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System.out.println("data == copy " + (data == copy));
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System.out.println(copy.hashCode() == data.hashCode());
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// 输出 1
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// 浅 Copy
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// 浅深主要在于对象类型
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System.out.println(copy.getValue());
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// 如果是浅拷贝的话
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// desc -> data.desc -> clone -> copy.desc == desc
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System.out.println(copy.getDesc() == desc);
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// 如果是深拷贝的话
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System.out.println(copy.getDesc().equals(desc));
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}
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}
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class Data extends Object implements Cloneable {
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private int value;
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private String desc;
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public int getValue() {
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return value;
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}
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public void setValue(int value) {
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this.value = value;
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}
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public String getDesc() {
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return desc;
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}
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public void setDesc(String desc) {
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this.desc = desc;
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}
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/**
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* 通常把 protected 访问性提升为 public
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* 强制调整为目标类型
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*
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* @return
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* @throws CloneNotSupportedException
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*/
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public Data clone() throws CloneNotSupportedException {
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Data copy = (Data) super.clone();
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// 原生类型没有浅深关系
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// 对象类型需要复制
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copy.desc = new String(this.desc);
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return copy;
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}
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// @Override
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// public int hashCode() {
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// return value;
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// }
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}

‎「一入 Java 深似海 」/代码/segmentfault/deep-in-java/stage-1/lesson-2/src/main/java/com/segmentfault/deep/in/java/EnumClassDemo.java

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package com.segmentfault.deep.in.java;
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import java.io.Serializable;
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import java.lang.reflect.Field;
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import java.lang.reflect.Member;
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import java.lang.reflect.Modifier;
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import java.util.stream.Collectors;
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import java.util.stream.Stream;
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public class EnumClassDemo {
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public static void main(String[] args) {
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// Q1: THREE 到底是第几个定义的
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// println(Counting.ONE);
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// println(Counting.FIVE);
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// Q3: 为什么枚举会输出成员名称
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// println(CountingEnum.ONE);
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// println(CountingEnum.FIVE);
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//
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// printEnumMeta(CountingEnum.ONE);
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// printEnumMeta(CountingEnum.FIVE);
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// 自定义实现 values()
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printCountingMembers();
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// Java 枚举字节码提升实现 values()
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printCountingEnumMembers();
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}
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// Q2: 能否输出所有的成员
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public static void println(Counting counting) {
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System.out.println(counting);
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}
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public static void println(CountingEnum countingEnum) {
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System.out.println(countingEnum);
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}
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public static void printEnumMeta(Enum enumeration) {
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// 说明任何枚举都扩展了 java.lang.Enum
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System.out.println("Enumeration type : " + enumeration.getClass());
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// Enum#name() = 成员名称
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// Enum#ordinal() = 成员定义位置
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System.out.println("member : " + enumeration.name());
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System.out.println("ordinal : " + enumeration.ordinal());
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// values() 方法是 Java 编译器给枚举提升的方式
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}
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public static void printCountingMembers() {
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Stream.of(Counting.values())
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.forEach(System.out::println);
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}
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public static void printCountingEnumMembers() {
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Stream.of(CountingEnum.values())
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.forEach(System.out::println);
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}
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}
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enum CountingEnum implements Cloneable {
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ONE(1) {
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@Override
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public String valueAsString() {
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return String.valueOf(this.getValue());
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}
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},
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TWO(2) {
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@Override
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public String valueAsString() {
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return String.valueOf(this.getValue());
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}
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},
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THREE(3) {
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@Override
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public String valueAsString() {
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return String.valueOf(this.getValue());
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}
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},
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FOUR(4) {
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@Override
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public String valueAsString() {
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return String.valueOf(this.getValue());
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}
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},
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FIVE(5) {
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@Override
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public String valueAsString() {
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return String.valueOf(this.getValue());
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}
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};
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private int value;
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/* private */ CountingEnum(int value) {
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this.value = value;
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}
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@Override
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public String toString() {
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return "CountingEnum : " + value;
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}
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public abstract String valueAsString();
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public int getValue() {
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return value;
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}
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}
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//class ExtendedEnum extends CountingEnum {
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//
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//}
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class ExtendedCounting extends Counting {
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private ExtendedCounting(int value) {
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super(value);
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}
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@Override
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public String valueAsString() {
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return toString();
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}
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}
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/**
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* 枚举类：计数
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* 强类型约束（相对于常量）
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*/
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abstract class Counting extends Data implements Cloneable {
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public static final Counting ONE = new Counting(1) {
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@Override
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public String valueAsString() {
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return String.valueOf(this.getValue());
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}
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};
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public static final Counting TWO = new Counting(2) {
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@Override
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public String valueAsString() {
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return String.valueOf(this.getValue());
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}
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};
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public static final Counting THREE = new Counting(3) {
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@Override
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public String valueAsString() {
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return String.valueOf(this.getValue());
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}
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};
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public static final Counting FOUR = new Counting(4) {
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@Override
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public String valueAsString() {
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return String.valueOf(this.getValue());
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}
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};
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public static final Counting FIVE = new Counting(5) {
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@Override
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public String valueAsString() {
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return String.valueOf(this.getValue());
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}
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};
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private int value;
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protected Counting(int value) {
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this.value = value;
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}
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@Override
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public int getValue() {
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return value;
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}
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public abstract String valueAsString();
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@Override
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public String toString() {
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return "Counting : " + value;
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}
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public static Counting[] values() {
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// Fields -> filter -> public static final fields -> get
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return Stream.of(Counting.class.getDeclaredFields())
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.filter(field -> {
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int modifiers = field.getModifiers();
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return Modifier.isPublic(modifiers) && Modifier.isStatic(modifiers) && Modifier.isFinal(modifiers);
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}).map(field -> {
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// Field -> Counting
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try {
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return (Counting) field.get(null);
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} catch (IllegalAccessException e) {
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throw new RuntimeException(e);
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}
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}).collect(Collectors.toList()).toArray(new Counting[0]);
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}
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}

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