package com.aqs;
import lombok.*;
import java.util.concurrent.atomic.*;
@Data
@Getter
@Setter
@AllArgsConstructor
@ToString
class User {
private String name;
//如果要为atomicReferenceFieldUpdater服务,必须加上volatile修饰
public volatile Integer age;
}
public class AtomicTest {
public static void main(String[] args) {
System.out.println("原子更新数值---------------");
AtomicInteger atomicInteger = new AtomicInteger();
int i1 = atomicInteger.incrementAndGet();
System.out.println("原子增加后为" + i1);
System.out.println("原子更新数组---------------");
int[] a = new int[3];
AtomicIntegerArray atomicIntegerArray = new AtomicIntegerArray(a);
int i = atomicIntegerArray.addAndGet(1, 3);
System.out.println("数组元素[" + 1 + "]增加后为" + i);
System.out.println("数组为" + atomicIntegerArray);
System.out.println("原子更新对象---------------");
User user1 = new User("ly1", 10);
User user2 = new User("ly2", 20);
User user3 = new User("ly3", 30);
AtomicReference<User> atomicReference = new AtomicReference<>(user1);
boolean b = atomicReference.compareAndSet(user2, user3);
System.out.println("更新" + (b ? "成功" : "失败"));
System.out.println("引用里值为"+atomicReference.get());
boolean b1 = atomicReference.compareAndSet(user1, user3);
System.out.println("更新" + (b1 ? "成功" : "失败"));
System.out.println("引用里值为"+atomicReference.get());
System.out.println("原子更新对象属性---------------");
User user4=new User("ly4",40);
AtomicReferenceFieldUpdater<User, Integer> atomicReferenceFieldUpdater = AtomicReferenceFieldUpdater.newUpdater(User.class, Integer.class, "age");
boolean b2 = atomicReferenceFieldUpdater.compareAndSet(user4, 41, 400);
System.out.println("更新"+(b2?"成功":"失败"));
System.out.println("引用里user4值为"+atomicReferenceFieldUpdater.get(user4));
boolean b3 = atomicReferenceFieldUpdater.compareAndSet(user4, 40, 400);
System.out.println("更新"+(b3?"成功":"失败"));
System.out.println("引用里user4值为"+atomicReferenceFieldUpdater.get(user4));
System.out.println("其他使用---------------");
User user5=new User("ly5",50);
User user6=new User("ly6",60);
User user7=new User("ly7",70);
AtomicMarkableReference<User> userAtomicMarkableReference=new AtomicMarkableReference<>(user5,true);
boolean b4 = userAtomicMarkableReference.weakCompareAndSet(user6, user7, true, false);
System.out.println("更新"+(b4?"成功":"失败"));
System.out.println("引用里值为"+userAtomicMarkableReference.getReference());
boolean b5 = userAtomicMarkableReference.weakCompareAndSet(user5, user7, false, true);
System.out.println("更新"+(b5?"成功":"失败"));
System.out.println("引用里值为"+userAtomicMarkableReference.getReference());
boolean b6 = userAtomicMarkableReference.weakCompareAndSet(user5, user7, true, false);
System.out.println("更新"+(b6?"成功":"失败"));
System.out.println("引用里值为"+userAtomicMarkableReference.getReference());
System.out.println("AtomicStampedReference使用---------------");
User user80=new User("ly8",80);
User user90=new User("ly9",90);
User user100=new User("ly10",100);
AtomicStampedReference<User> userAtomicStampedReference=new AtomicStampedReference<>(user80,80);//版本80
//...每次更改stamp都加1
//这里假设中途被改成81了
boolean b7 = userAtomicStampedReference.compareAndSet(user80, user100,81,90);
System.out.println("更新"+(b7?"成功":"失败"));
System.out.println("引用里值为"+userAtomicStampedReference.getReference());
boolean b8 = userAtomicStampedReference.compareAndSet(user80, user100,80,90);
System.out.println("更新"+(b8?"成功":"失败"));
System.out.println("引用里值为"+userAtomicStampedReference.getReference());
}
}
/*
原子更新数值---------------
原子增加后为1
原子更新数组---------------
数组元素[1]增加后为3
数组为[0, 3, 0]
原子更新对象---------------
更新失败
引用里值为User(name=ly1, age=10)
更新成功
引用里值为User(name=ly3, age=30)
原子更新对象属性---------------
更新失败
引用里user4值为40
更新成功
引用里user4值为400
其他使用---------------
更新失败
引用里值为User(name=ly5, age=50)
更新失败
引用里值为User(name=ly5, age=50)
更新成功
引用里值为User(name=ly7, age=70)
AtomicStampedReference使用---------------
更新失败
引用里值为User(name=ly8, age=80)
更新成功
引用里值为User(name=ly10, age=100)
Process finished with exit code 0
*/
2022年12月12日 15:58 周一
如上，Eden区内存几乎被分配完全（即使程序什么都不做，新生代也会使用2000多K）
在给allocation2分配内存之前，Eden区内存几乎已经被分配完。所以当Eden区没有足够空间进行分配时，虚拟机将发起一次MinorGC。GC期间虚拟机又发现allocation1无法存入空间，所以只好通过分配担保机制，把新生代的对象，提前转移到老年代去，老年代的空间足够存放allocation1，所以不会出现Full GC（这里可能是之前的说法，可能只是要表达老年代的GC，而不是Full GC(整堆GC) ） 
1.8之后整个永久代改名叫"元空间"，且移到了本地内存中
