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[add] add dynamic type examples in jvm module.
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‎README.md

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2020
- [java-multithread](/java-multithread):多线程模块的 Java 源码
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- [java-container](/java-container):容器类模块的 Java 源码
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- [java-io](/java-io):IO 模块的 Java 源码
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- [java-jvm](/java-jvm): JVM 模块的 Java 源码
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- [java8](/java8): Java 8 模块的源码
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# 博客文档
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计划将这个仓库进行重构，逐步扩充并实现下面的功能。
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* [x] 整理成 maven 的结构，使用聚合和继承特性(2016.4.12完成)
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* [x] 整理成 maven 的结构，使用聚合和继承特性(2016.4.12 完成)
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* [ ] 原有的 Java SE 部分代码重构为 java-base 模块，并逐步上传代码
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* [x] 多线程部分使用 java-multithread 模块(2016.4.17完成雏形)
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* [x] 多线程部分使用 java-multithread 模块(2016.4.17 完成雏形)
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* [ ] 容器类部分使用模块 java-container
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* [ ] IO 部分使用模块 java-io
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* [ ] Java 虚拟机相关部分使用模块 java-jvm
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* [x] Java 虚拟机相关部分使用模块 java-jvm(2017.3.20 完成雏形)
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* [ ] Java 8 新特性使用模块 java8(正在进行)
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‎java-jvm/src/main/java/com/brianway/learning/java/jvm/dynamictype/GrandFatherCaller.java

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package com.brianway.learning.java.jvm.dynamictype;
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import static java.lang.invoke.MethodHandles.lookup;
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import java.lang.invoke.MethodHandle;
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import java.lang.invoke.MethodType;
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/**
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* Created by brian on 17/3/20.
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* 使用 MethodHandle 来访问祖类方法
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* TODO 为什么打印出来的是 "i am father" 而不是 "i am grandfather"?
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*/
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public class GrandFatherCaller {
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class GrandFather {
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void thinking() {
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System.out.println("i am grandfather");
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}
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}
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class Father extends GrandFather {
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void thinking() {
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System.out.println("i am father");
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}
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}
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class Son extends Father {
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void thinking() {
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try {
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MethodType mt = MethodType.methodType(void.class);
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MethodHandle mh = lookup().findSpecial(
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GrandFather.class, "thinking", mt, Son.class);
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mh.invoke(this);
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} catch (Throwable throwable) {
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throwable.printStackTrace();
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}
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}
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}
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public static void main(String[] args) {
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(new GrandFatherCaller().new Son()).thinking();
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}
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}

‎java-jvm/src/main/java/com/brianway/learning/java/jvm/dynamictype/InvokeDynamicTest.java

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package com.brianway.learning.java.jvm.dynamictype;
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import static java.lang.invoke.MethodHandles.lookup;
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import java.lang.invoke.CallSite;
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import java.lang.invoke.ConstantCallSite;
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import java.lang.invoke.MethodHandle;
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import java.lang.invoke.MethodHandles;
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import java.lang.invoke.MethodType;
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/**
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* Created by brian on 17/3/20.
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* invokedynamic 指令演示
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*/
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public class InvokeDynamicTest {
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public static void main(String[] args) throws Throwable {
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INDY_BootstrapMethod().invokeExact("brianway");
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}
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public static void testMethod(String s) {
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System.out.println("hello String:" + s);
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}
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public static CallSite BootstrapMethod(
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MethodHandles.Lookup lookup, String name, MethodType mt)
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throws Throwable {
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return new ConstantCallSite(lookup.findStatic(InvokeDynamicTest.class, name, mt));
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}
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private static MethodType MT_BootstrapMethod() {
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return MethodType.fromMethodDescriptorString(
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"(Ljava/lang/invoke/MethodHandles$Lookup;" +
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"Ljava/lang/String;Ljava/lang/invoke/MethodType;)" +
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"Ljava/lang/invoke/CallSite;", null
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);
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}
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private static MethodHandle MH_BootstrapMethod() throws Throwable {
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return lookup().findStatic(InvokeDynamicTest.class, "BootstrapMethod",
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MT_BootstrapMethod());
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}
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private static MethodHandle INDY_BootstrapMethod() throws Throwable {
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CallSite cs = (CallSite) MH_BootstrapMethod().invokeWithArguments(
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lookup(),
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"testMethod",
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MethodType.fromMethodDescriptorString(
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"(Ljava/lang/String;)V", null
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));
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return cs.dynamicInvoker();
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}
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}

‎java-jvm/src/main/java/com/brianway/learning/java/jvm/dynamictype/MethodHandleTest.java

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package com.brianway.learning.java.jvm.dynamictype;
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import static java.lang.invoke.MethodHandles.lookup;
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import java.lang.invoke.MethodHandle;
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import java.lang.invoke.MethodType;
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/**
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* Created by brian on 17/3/20.
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* MethodHandle 演示
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*/
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public class MethodHandleTest {
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static class ClassA {
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public void println(String s) {
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System.out.println("classA " + s);
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}
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}
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public static void main(String[] args) throws Throwable {
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Object obj = System.currentTimeMillis() % 2 == 0 ? System.out : new ClassA();
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getPrintlnMH(obj).invokeExact("brianway");
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}
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private static MethodHandle getPrintlnMH(Object receiver) throws Throwable {
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// 方法类型
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MethodType mt = MethodType.methodType(void.class, String.class);
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return lookup().findVirtual(receiver.getClass(), "println", mt)
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.bindTo(receiver);
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}
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}

‎java-jvm/src/main/java/com/brianway/learning/java/jvm/methodinvoke/Dispatch.java

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package com.brianway.learning.java.jvm.methodinvoke;
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/**
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* Created by brian on 17/3/20.
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* 单分派、多分派演示
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*/
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public class Dispatch {
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static class QQ {
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}
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static class _360 {
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}
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public static class Father {
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public void hardChoice(QQ arg) {
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System.out.println("father choose qq");
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}
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public void hardChoice(_360 arg) {
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System.out.println("father choose 360");
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}
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}
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public static class Son extends Father {
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public void hardChoice(QQ arg) {
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System.out.println("son choose qq");
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}
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public void hardChoice(_360 arg) {
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System.out.println("son choose 360");
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}
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}
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public static void main(String[] args) {
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Father father = new Father();
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Father son = new Son();
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father.hardChoice(new _360());
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son.hardChoice(new QQ());
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}
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}
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/*
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father choose 360
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son choose qq
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*/

‎java-jvm/src/main/java/com/brianway/learning/java/jvm/methodinvoke/DynamicDispatch.java

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package com.brianway.learning.java.jvm.methodinvoke;
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/**
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* Created by brian on 17/3/20.
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* 方法动态分派演示
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*/
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public class DynamicDispatch {
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static abstract class Human {
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protected abstract void sayHello();
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}
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static class Man extends Human {
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@Override
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protected void sayHello() {
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System.out.println("man say hello");
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}
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}
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static class Woman extends Human {
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@Override
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protected void sayHello() {
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System.out.println("woman say hello");
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}
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}
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public static void main(String[] args) {
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Human man = new Man();
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Human woman = new Woman();
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man.sayHello();
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woman.sayHello();
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man = new Woman();
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man.sayHello();
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}
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}
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/*
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man say hello
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woman say hello
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woman say hello
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*/

‎java-jvm/src/main/java/com/brianway/learning/java/jvm/methodinvoke/StaticDispatch.java

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package com.brianway.learning.java.jvm.methodinvoke;
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/**
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* Created by brian on 17/3/20.
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* 方法静态分派演示
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* Method Overload Resolution
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*/
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public class StaticDispatch {
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static abstract class Human {
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}
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static class Man extends Human {
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}
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static class Woman extends Human {
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}
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public void sayHello(Human guy) {
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System.out.println("hello,guy!");
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}
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public void sayHello(Man guy) {
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System.out.println("hello,gentleman!");
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}
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public void sayHello(Woman guy) {
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System.out.println("hello,lady!");
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}
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public static void main(String[] args) {
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Human man = new Man();
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Human woman = new Woman();
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StaticDispatch sr = new StaticDispatch();
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sr.sayHello(man);
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sr.sayHello(woman);
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sr.sayHello((Man)man);
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sr.sayHello((Woman) woman);
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}
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}
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/*
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hello,guy!
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hello,guy!
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hello,gentleman!
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hello,lady!
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*/

‎java-jvm/src/main/java/com/brianway/learning/java/jvm/methodinvoke/StaticResolution.java

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package com.brianway.learning.java.jvm.methodinvoke;
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/**
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* Created by brian on 17/3/20.
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* 方法静态解析演示
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* javac -verbose StaticResolution.java
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* javap -verbose StaticResolution
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*/
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public class StaticResolution {
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public static void sayHello() {
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System.out.println("hello world");
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}
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public static void main(String[] args) {
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StaticResolution.sayHello();
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}
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}

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