demo

chenzhuo@picooc.com · chenzhuo@picooc.com · commit 0fca7b7ae186 · 2018-12-23T20:51:25.000+08:00
diff --git a/src/main/java/com/sun/jvm/Jvm/SimpleHeadpAlloc.java b/src/main/java/com/sun/jvm/Jvm/SimpleHeadpAlloc.java
@@ -1,5 +1,8 @@
 package com.sun.jvm.Jvm;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 /**
  * @ClassName SimpleHeadpAlloc
  * @Despacito TODO
@@ -8,6 +11,8 @@
  * -Xmx20m -Xms5m -XX:+PrintCommandLineFlags -XX:+PrintGCDetails -XX:+UseSerialGC
  **/
 public class SimpleHeadpAlloc {
+  /*  public static final Logger logger = LoggerFactory.getLogger(SimpleHeadpAlloc.class);*/
+    public final  double aDouble = 555D;
     public static void main(String[] args) throws InterruptedException {
         getOut();
         byte[] b = new byte[1024 * 1024];
diff --git a/src/main/java/com/sun/jvm/Jvm/SoftReFQ.java b/src/main/java/com/sun/jvm/Jvm/SoftReFQ.java
@@ -0,0 +1,91 @@
+package com.sun.jvm.Jvm;
+
+import java.lang.ref.ReferenceQueue;
+import java.lang.ref.SoftReference;
+
+/**
+ * @ClassName SoftReFQ
+ * @Despacito TODO
+ * @Author chenzhuo
+ * @Version 1.0
+ * -Xmx10M -XX:+PrintGC
+ * 没有回收引用
+ *
+ **/
+public class SoftReFQ {
+    public static class User {
+        private int id;
+        private String name;
+        public User(int id, String name) {
+            this.id = id;
+            this.name = name;
+        }
+
+        @Override
+        public String toString() {
+            return "User{" +
+                    "id=" + id +
+                    ", name='" + name + '\'' +
+                    '}';
+        }
+    }
+
+    static ReferenceQueue<User> queue = null;
+
+    public static class CheckReQueue extends Thread {
+        public void run() {
+            while (true) {
+                if (queue != null) {
+                    UserSoftRereence userSoftRereence = null;
+                    try {
+                    /*    System.out.println("userReferenceQueue:"+
+                                userSoftRereence.get());*/
+                        userSoftRereence = (UserSoftRereence) queue.remove();
+                    } catch (InterruptedException e) {
+                        e.printStackTrace();
+                    }
+                    if (userSoftRereence != null) {
+                        System.out.println("user id" +
+                                userSoftRereence.userId + " is delete");
+                    }
+                }
+            }
+        }
+    }
+
+    /**
+     * 强引用 不会回收
+     * 软引用 比强引用弱一点，内存不足的时候就会被回收
+     * 弱信用 回收,gc的时候发现就会回收
+     * 虚引用 最弱
+     */
+    public static class UserSoftRereence extends SoftReference<User> {
+        int userId;
+
+        public UserSoftRereence(User referent, ReferenceQueue<? super User> queue) {
+            super(referent);
+            userId = referent.id;
+        }
+    }
+
+    public static void main(String[] args) throws InterruptedException {
+        Thread thread = new CheckReQueue();
+        thread.setDaemon(true);
+        thread.start();
+        User user = new User(1,"chenzhuo");
+        queue = new ReferenceQueue<>();
+        UserSoftRereence userSoftRereence
+                 = new UserSoftRereence(user,queue);
+        user = null;
+        System.out.println(userSoftRereence.get());
+        System.gc();
+        System.out.println("After GC:");
+        System.out.println(userSoftRereence.get());
+        System.out.println("尝试创建字节 和回收");
+        byte[] b = new byte[7*1024*925];
+        System.gc();
+        System.out.println(userSoftRereence.get());
+        Thread.sleep(1000);
+    }
+
+}
diff --git a/src/main/java/com/sun/jvm/Jvm/SoftRef.java b/src/main/java/com/sun/jvm/Jvm/SoftRef.java
@@ -0,0 +1,46 @@
+package com.sun.jvm.Jvm;
+
+import java.lang.ref.SoftReference;
+
+/**
+ * @ClassName SoftRef
+ * @Despacito TODO
+ * @Author chenzhuo
+ * @Version 1.0
+ **/
+public class SoftRef {
+    public static class User {
+        private int id;
+        private String name;
+
+        public User(int id, String name) {
+            this.id = id;
+            this.name = name;
+        }
+
+        @Override
+        public String toString() {
+            return "User{" +
+                    "id=" + id +
+                    ", name='" + name + '\'' +
+                    '}';
+        }
+    }
+
+    public static void main(String[] args) {
+        User user = new User(1, "cz");
+        SoftReference<User>
+                userSoftReference = new SoftReference<>(user);
+        user = null;
+
+        System.out.println(userSoftReference.get());
+        System.gc();
+        System.out.println("After GC:");
+        System.out.println(userSoftReference.get());
+
+        byte[] b = new byte[7 * 1024 * 925];
+        System.gc();
+        System.out.println(userSoftReference.get());
+
+    }
+}
