[add] add examples of class loading in jvm module

brianway · brianway · commit 90bfef78d36c · 2017-03-20T15:48:58.000+08:00
diff --git a/java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/ClassLoaderTest.java b/java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/ClassLoaderTest.java
@@ -0,0 +1,40 @@
+package com.brianway.learning.java.jvm.classloading;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+/**
+ * Created by brian on 17/3/20.
+ * 不同的类加载器对 instanceof 关键字运算结果的影响
+ */
+public class ClassLoaderTest {
+    public static void main(String[] args) throws Exception {
+        ClassLoader myLoader = new ClassLoader() {
+            @Override
+            public Class<?> loadClass(String name) throws ClassNotFoundException {
+                try {
+                    String fileName = name.substring(name.lastIndexOf(".") + 1) + ".class";
+
+                    InputStream is = getClass().getResourceAsStream(fileName);
+                    if (is == null) {
+                        return super.loadClass(name);
+                    }
+                    byte[] b = new byte[is.available()];
+                    is.read(b);
+                    return defineClass(name, b, 0, b.length);
+                } catch (IOException e) {
+                    throw new ClassNotFoundException(name);
+                }
+            }
+        };
+
+        Object obj = myLoader.loadClass("com.brianway.learning.java.jvm.classloading.ClassLoaderTest").newInstance();
+        System.out.println(obj.getClass());
+        System.out.println(obj instanceof com.brianway.learning.java.jvm.classloading.ClassLoaderTest);
+    }
+}
+
+/*
+class com.brianway.learning.java.jvm.classloading.ClassLoaderTest
+false
+ */
diff --git a/java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/ClinitOrder.java b/java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/ClinitOrder.java
@@ -0,0 +1,27 @@
+package com.brianway.learning.java.jvm.classloading;
+
+/**
+ * Created by brian on 17/3/20.
+ * <clinit>() 方法执行顺序
+ */
+public class ClinitOrder {
+    static class Parent {
+        public static int A = 1;
+
+        static {
+            System.out.println("execute before A = 2, A now is " + A);
+            A = 2;
+        }
+    }
+
+    static class Sub extends Parent {
+        public static int B = A;
+    }
+
+
+    public static void main(String[] args) {
+        System.out.println(Sub.B);
+    }
+}
+
+
diff --git a/java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/ConstClass.java b/java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/ConstClass.java
@@ -1,4 +1,4 @@
-package com.brianway.learning.java.jvm.classfile;
+package com.brianway.learning.java.jvm.classloading;
 
 /**
  * Created by brian on 17/3/19.
diff --git a/java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/DeadLoopClass.java b/java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/DeadLoopClass.java
@@ -0,0 +1,30 @@
+package com.brianway.learning.java.jvm.classloading;
+
+/**
+ * Created by brian on 17/3/20.
+ * 字段解析
+ * 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
+ */
+public class DeadLoopClass {
+    static {
+        if (true) {
+            System.out.println(Thread.currentThread() + " init DeadLoopClass");
+            while (true) {
+
+            }
+        }
+    }
+
+    public static void main(String[] args) {
+        Runnable script = () -> {
+            System.out.println(Thread.currentThread() + " start");
+            DeadLoopClass dlc = new DeadLoopClass();
+            System.out.println(Thread.currentThread() + " run over");
+        };
+
+        Thread thread1 = new Thread(script);
+        Thread thread2 = new Thread(script);
+        thread1.start();
+        thread2.start();
+    }
+}
diff --git a/java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/FieldResolution.java b/java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/FieldResolution.java
@@ -0,0 +1,32 @@
+package com.brianway.learning.java.jvm.classloading;
+
+/**
+ * Created by brian on 17/3/20.
+ * 字段解析
+ * 如果注释了 Sub 类中的 "public static int A = 4",会编译错误
+ */
+public class FieldResolution {
+    interface Interface0 {
+        int A = 0;
+    }
+
+    interface Interface1 extends Interface0 {
+        int A = 1;
+    }
+
+    interface Interface2 {
+        int A = 2;
+    }
+
+    static class Parent implements Interface1 {
+        public static int A = 3;
+    }
+
+    static class Sub extends Parent implements Interface2 {
+        public static int A = 4;// 注释此句试试
+    }
+
+    public static void main(String[] args) {
+        System.out.println(Sub.A);
+    }
+}
diff --git a/java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/NoInitialization.java b/java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/NoInitialization.java
@@ -1,4 +1,4 @@
-package com.brianway.learning.java.jvm.classfile;
+package com.brianway.learning.java.jvm.classloading;
 
 /**
  * Created by brian on 17/3/19.
diff --git a/java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/SimpleClass.java b/java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/SimpleClass.java
@@ -1,4 +1,4 @@
-package com.brianway.learning.java.jvm.classfile;
+package com.brianway.learning.java.jvm.classloading;
 
 /**
  * Created by brian on 17/3/15.
diff --git a/java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/SubClass.java b/java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/SubClass.java
@@ -1,4 +1,4 @@
-package com.brianway.learning.java.jvm.classfile;
+package com.brianway.learning.java.jvm.classloading;
 
 /**
  * Created by brian on 17/3/19.
diff --git a/java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/SuperClass.java b/java-jvm/src/main/java/com/brianway/learning/java/jvm/classloading/SuperClass.java
@@ -1,4 +1,4 @@
-package com.brianway.learning.java.jvm.classfile;
+package com.brianway.learning.java.jvm.classloading;
 
 /**
  * Created by brian on 17/3/19.

Original file line number	Diff line number	Diff line change
`@@ -1,4 +1,4 @@`
`1`		`-package com.brianway.learning.java.jvm.classfile;`
	`1`	`+package com.brianway.learning.java.jvm.classloading;`
`2`	`2`
`3`	`3`	`/**`
`4`	`4`	`* Created by brian on 17/3/19.`