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[add] add examples of class loading in jvm module · JavaDevelopRep/java-learning@90bfef7 · GitHub

/ java-learning Public
forked from brianway/java-learning

Commit 90bfef7

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[add] add examples of class loading in jvm module
1 parent 6840e59 commit 90bfef7

9 files changed

Lines changed: 134 additions & 5 deletions

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‎java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/ClassLoaderTest.java‎

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package com.brianway.learning.java.jvm.classloading;
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import java.io.IOException;
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import java.io.InputStream;
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/**
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* Created by brian on 17/3/20.
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* 不同的类加载器对 instanceof 关键字运算结果的影响
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*/
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public class ClassLoaderTest {
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public static void main(String[] args) throws Exception {
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ClassLoader myLoader = new ClassLoader() {
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@Override
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public Class<?> loadClass(String name) throws ClassNotFoundException {
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try {
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String fileName = name.substring(name.lastIndexOf(".") + 1) + ".class";
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InputStream is = getClass().getResourceAsStream(fileName);
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if (is == null) {
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return super.loadClass(name);
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}
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byte[] b = new byte[is.available()];
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is.read(b);
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return defineClass(name, b, 0, b.length);
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} catch (IOException e) {
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throw new ClassNotFoundException(name);
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}
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}
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};
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Object obj = myLoader.loadClass("com.brianway.learning.java.jvm.classloading.ClassLoaderTest").newInstance();
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System.out.println(obj.getClass());
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System.out.println(obj instanceof com.brianway.learning.java.jvm.classloading.ClassLoaderTest);
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}
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}
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/*
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class com.brianway.learning.java.jvm.classloading.ClassLoaderTest
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false
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*/

‎java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/ClinitOrder.java‎

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package com.brianway.learning.java.jvm.classloading;
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/**
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* Created by brian on 17/3/20.
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* <clinit>() 方法执行顺序
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*/
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public class ClinitOrder {
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static class Parent {
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public static int A = 1;
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static {
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System.out.println("execute before A = 2, A now is " + A);
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A = 2;
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}
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}
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static class Sub extends Parent {
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public static int B = A;
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}
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public static void main(String[] args) {
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System.out.println(Sub.B);
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}
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}
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java-jvm/src/main/java/com/brianway/learning/java/jvm/classfile/ConstClass.java renamed to java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/ConstClass.java

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package com.brianway.learning.java.jvm.classfile;
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package com.brianway.learning.java.jvm.classloading;
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/**
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* Created by brian on 17/3/19.

‎java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/DeadLoopClass.java‎

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package com.brianway.learning.java.jvm.classloading;
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/**
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* Created by brian on 17/3/20.
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* 字段解析
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* 多个线程同时初始化一个类,只有一个线程会执行 <clinit>()方法,其他被阻塞
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*/
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public class DeadLoopClass {
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static {
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if (true) {
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System.out.println(Thread.currentThread() + " init DeadLoopClass");
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while (true) {
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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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Runnable script = () -> {
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System.out.println(Thread.currentThread() + " start");
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DeadLoopClass dlc = new DeadLoopClass();
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System.out.println(Thread.currentThread() + " run over");
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};
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Thread thread1 = new Thread(script);
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Thread thread2 = new Thread(script);
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thread1.start();
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thread2.start();
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}
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}

‎java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/FieldResolution.java‎

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package com.brianway.learning.java.jvm.classloading;
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/**
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* Created by brian on 17/3/20.
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* 字段解析
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* 如果注释了 Sub 类中的 "public static int A = 4",会编译错误
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*/
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public class FieldResolution {
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interface Interface0 {
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int A = 0;
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}
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interface Interface1 extends Interface0 {
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int A = 1;
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}
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interface Interface2 {
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int A = 2;
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}
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static class Parent implements Interface1 {
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public static int A = 3;
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}
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static class Sub extends Parent implements Interface2 {
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public static int A = 4;// 注释此句试试
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}
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public static void main(String[] args) {
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System.out.println(Sub.A);
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}
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}

java-jvm/src/main/java/com/brianway/learning/java/jvm/classfile/NoInitialization.java renamed to java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/NoInitialization.java

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package com.brianway.learning.java.jvm.classfile;
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package com.brianway.learning.java.jvm.classloading;
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/**
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* Created by brian on 17/3/19.

java-jvm/src/main/java/com/brianway/learning/java/jvm/classfile/SimpleClass.java renamed to java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/SimpleClass.java

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package com.brianway.learning.java.jvm.classfile;
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package com.brianway.learning.java.jvm.classloading;
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/**
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* Created by brian on 17/3/15.

java-jvm/src/main/java/com/brianway/learning/java/jvm/classfile/SubClass.java renamed to java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/SubClass.java

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package com.brianway.learning.java.jvm.classfile;
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package com.brianway.learning.java.jvm.classloading;
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/**
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* Created by brian on 17/3/19.

java-jvm/src/main/java/com/brianway/learning/java/jvm/classfile/SuperClass.java renamed to java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/SuperClass.java

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package com.brianway.learning.java.jvm.classfile;
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package com.brianway.learning.java.jvm.classloading;
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/**
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* Created by brian on 17/3/19.

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