安全发布对象
发布对象：
import com.example.annoations.NotThreadSafe;
import lombok.extern.slf4j.Slf4j;
import java.util.Arrays;
@Slf4j
@NotThreadSafe
public class UnsafePublish {
private String[] states={"a","b","c"};
public String [] getStates(){
return states;
}
public static void main(String[] args) {
UnsafePublish unsafePublish=new UnsafePublish();
log.info("{}", Arrays.toString(unsafePublish.getStates()));
unsafePublish.getStates()[0]="d";
log.info("{}",Arrays.toString(unsafePublish.getStates()));
}
}
import com.example.annoations.NotRecommend;
import com.example.annoations.NotThreadSafe;
import lombok.extern.slf4j.Slf4j;
@Slf4j
@NotThreadSafe
@NotRecommend
public class Escape {
public int thisCanBeEscape=0;
public Escape(){
new InnerClass();
}
private class InnerClass{
public InnerClass(){
log.info("{}",Escape.this.thisCanBeEscape);
}
}
public static void main(String[] args) {
new Escape();
}
}
安全发布对象：
import com.example.annoations.NotThreadSafe;
//懒汉模式，单例的实例在第一次使用的时候进行创建
@NotThreadSafe
public class SingletonExample1 {
//私有的构造函数
private SingletonExample1 (){
}
//单例对象
private static SingletonExample1 instance=null;
//静态的工厂方法
public static SingletonExample1 getInstance(){
if(instance==null){
instance=new SingletonExample1();
}
return instance;
}
}
import com.example.annoations.ThreadSafe;
//恶汉模式，单例实例在类装载使用时创建
@ThreadSafe
public class SingletonExample2 {
//私有构造函数
private SingletonExample2(){
}
//单例对象
private static SingletonExample2 instance=new SingletonExample2();
//静态的工厂方法
public static SingletonExample2 getInstance(){
return instance;
}
}
//懒汉模式，单例的实例在第一次使用的时候进行创建
@NotThreadSafe
public class SingletonExample3 {
//私有的构造函数
private SingletonExample3 (){
}
//单例对象
private static SingletonExample3 instance=null;
//静态的工厂方法
public static synchronized SingletonExample3 getInstance(){
if(instance==null){
instance=new SingletonExample3();
}
return instance;
}
}
线程不安全
import com.example.annoations.NotThreadSafe;
//懒汉模式，双重同步锁的单例模式，单例的实例在第一次使用的时候进行创建
@NotThreadSafe
public class SingletonExample4 {
//私有的构造函数
private SingletonExample4 (){
}
//1.memory=allocate(),分配内存空间
//2.ctorInstance()初始对象
//3.instance=memory 设置instance指向刚分配的内存
//JVM和cpu优化，发生了指令重拍
//1.memory=allocate(),分配内存空间
//3.instance=memory 设置instance指向刚分配的内存
//2.ctorInstance()初始对象
//单例对象
private static SingletonExample4 instance=null;
//静态的工厂方法
public static SingletonExample4 getInstance(){
if(instance==null){//双重检测机制
synchronized (SingletonExample4.class){ //同步锁
if(instance==null){ //多线程发生指令重拍
instance=new SingletonExample4();
}
}
}
return instance;
}
}
volatile+双重检测，线程安全
import com.example.annoations.ThreadSafe;
@ThreadSafe
public class SingletonExample5 {
//私有的构造函数
private SingletonExample5(){
}
//单例对象 volatile+双重检测机制
private volatile static SingletonExample5 instance=null;
//静态的工厂方法
public static SingletonExample5 getInstance(){
if(instance==null){//双重检测机制
synchronized (SingletonExample5.class){ //同步锁
if(instance==null){ //多线程发生指令重拍
instance=new SingletonExample5();
}
}
}
return instance;
}
}
//饿汉模式
public class SingletonExample6 {
//私有构造函数
private SingletonExample6(){
}
//单例对象
private static SingletonExample6 instance=null;
static {
instance=new SingletonExample6();
}
//静态工厂的方法
public static SingletonExample6 getInstance(){
return instance;
}
public static void main(String[] args) {
System.out.println(getInstance().hashCode());
System.out.println(getInstance().hashCode());
}
}
import com.example.annoations.ThreadSafe;
//枚举模式 最安全
@ThreadSafe
public class SingletonExample7 {
//私有构造函数
private SingletonExample7(){
}
public static SingletonExample7 getInstance(){
return Singleton.INSTANCE.getInstance();
}
public enum Singleton{
INSTANCE;
//构造函数JVM保证这个方法只能被调用一次
private SingletonExample7 singleton;
Singleton(){
singleton=new SingletonExample7();
}
public SingletonExample7 getInstance(){
return singleton;
}
}
}
import com.example.annoations.NotThreadSafe;
import com.google.common.collect.Maps;
import lombok.extern.slf4j.Slf4j;
import java.util.Map;
@Slf4j
@NotThreadSafe
public class ImmutableExample1{
private final static Integer a=1;
private final static String b="2";
private final static Map<Integer,Integer> map = Maps.newHashMap();
static {
map.put(1,2);
map.put(3,4);
map.put(5,6);
}
//值可修改
public static void main(String[] args) {
map.put(1,3);
log.info("{}",map.get(1));
}
private void test(final int a){
// a=1;
}
}
另外的不可变对象 
import com.example.annoations.ThreadSafe;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
@ThreadSafe //线程安全
public class ImmutableExample3 {
private final static ImmutableList list=ImmutableList.of(1,2,3);
private final static ImmutableSet set=ImmutableSet.copyOf(list);
private final static ImmutableMap<Integer,Integer> map=ImmutableMap.of(1,2,3,4);
private final static ImmutableMap<Integer,Integer> map2=
ImmutableMap.<Integer,Integer>builder().put(3,4).put(5,6).build();
public static void main(String[] args) {
list.add(4);
map.put(1,4);
System.out.println(map2.get(2));
}
}
import com.google.common.collect.Maps;
import java.util.Collections;
import java.util.Map;
public class ImmutableExample2 {
private static Map<Integer,Integer> map = Maps.newHashMap();
static {
map.put(1,2);
map.put(3,4);
map.put(5,6);
map= Collections.unmodifiableMap(map);
}
//值可修改
public static void main(String[] args) {
map.put(1,3);
log.info("{}",map.get(1));
}
}
