package Single;
/*
餓漢式
?*/
public class Demo01 {
????public static void main(String[] args) {
????????HungrySingle h1 = HungrySingle.getInstance();
????????HungrySingle h2 = HungrySingle.getInstance();
????????System.out.println(h1 == h2);//true
????}
}

class HungrySingle{
????private static HungrySingle INT = new HungrySingle();

????private HungrySingle(){}

????public static HungrySingle getInstance(){
????????return INT;
????}
}

?

package Single;

public class Demo02 {
????public static void main(String[] args) {
????????LazySingle l1 = LazySingle.getIntance();
????????LazySingle l2 = LazySingle.getIntance();

????????System.out.println(l1 == l2);//true
????}
}

class LazySingle{
????private static LazySingle LAZ = null;

????private LazySingle(){}

????public static LazySingle getIntance(){
????????if (LAZ == null){
????????????LAZ = new LazySingle(); ?//當真正需要這個類的時候在創建這個類
????????}
????????return LAZ;
????}
}

?

package Single;

public class Demo02_p {
????public static void main(String[] args) {
????????LazySingle l1 = LazySingle.getIntance();
????????LazySingle l2 = LazySingle.getIntance();

????????System.out.println(l1 == l2);//true
????}
}

class LazySingle2{
????private static LazySingle2 LAZ = null;

????private LazySingle2(){}

????//懶漢式的線程不安全問題解決
????public static synchronized LazySingle2 getIntance(){
????????if (LAZ == null){
????????????LAZ = new LazySingle2(); ?//當真正需要這個類的時候在創建這個類
????????}
????????return LAZ;
????}
}

?

package Single;

public class Demo03 {

????public static void main(String[] args) {
????????SingletonOld so1 = SingletonOld.so;
????????System.out.println(so1);
????????SingletonOld so2 = SingletonOld.so;
????????System.out.println(so2);
????????System.out.println(so1 == so2);//true

// ???SingletonOld.so = null;
????}
}

class SingletonOld {
????/*
????1.私有化構造函數
????2.將對象實例化為final
?????*/
????private SingletonOld() {
????}
????public static final SingletonOld so = new SingletonOld();
}

?

線程協作：不同線程執行不同的任務，如果這些任務有某種聯系，那么線程之間必須能通過?通信，協調完成工作。根據生產者與消費者去理解：

?

垃圾回收機制：

所謂的垃圾回收機制，即在java中使用new關鍵字創建對象時，都會在堆內存中為之分配一塊內存，用于保護對象，當此內存不在被任何引用變量引用時，這塊內存就變成了垃圾，java引入垃圾回收機制（Garbage Collection）來處理垃圾，他是一個動態存儲管理技術，由java虛擬機自動回收垃圾對象所占的內存空間，不需要程序代碼來顯式釋放。