Singleton

whatsmars-common/src/test/java/org/hongxi/java/util/lang/Animal.java → whatsmars-common/src/test/java/org/hongxi/java/util/lang/oop/Animal.java

-package org.hongxi.java.util.lang;
+package org.hongxi.java.util.lang.oop;
 
 /**
  * @author shenhongxi 2019/8/11

whatsmars-common/src/test/java/org/hongxi/java/util/lang/Cat.java → whatsmars-common/src/test/java/org/hongxi/java/util/lang/oop/Cat.java

-package org.hongxi.java.util.lang;
+package org.hongxi.java.util.lang.oop;
 
 /**
  * @author shenhongxi 2019/8/11

whatsmars-common/src/test/java/org/hongxi/java/util/lang/ChinaCat.java → whatsmars-common/src/test/java/org/hongxi/java/util/lang/oop/ChinaCat.java

-package org.hongxi.java.util.lang;
+package org.hongxi.java.util.lang.oop;
 
 /**
  * @author shenhongxi 2019/8/11

whatsmars-common/src/test/java/org/hongxi/java/util/lang/singleton/EagerSingleton.java

+package org.hongxi.java.util.lang.singleton;
+
+/**
+ * @author shenhongxi 2019/8/11
+ */
+public class EagerSingleton {
+
+    private static EagerSingleton instance = new EagerSingleton();
+
+    private EagerSingleton() {}
+
+    public static EagerSingleton getInstance() {
+        return instance;
+    }
+}

whatsmars-common/src/test/java/org/hongxi/java/util/lang/singleton/EnumSingleton.java

+package org.hongxi.java.util.lang.singleton;
+
+/**
+ * @author shenhongxi 2019/8/11
+ */
+public enum EnumSingleton {
+
+    INSTANCE;
+
+    public String config;
+
+    public String getConfig() {
+        return config;
+    }
+
+    public void setConfig(String config) {
+        this.config = config;
+    }
+}

whatsmars-common/src/test/java/org/hongxi/java/util/lang/singleton/InnerClassSingleton.java

+package org.hongxi.java.util.lang.singleton;
+
+/**
+ * @author shenhongxi 2019/8/11
+ */
+public class InnerClassSingleton {
+
+    private InnerClassSingleton() {}
+
+    private static class SingletonHolder {
+        private static final InnerClassSingleton instance = new InnerClassSingleton();
+    }
+
+    public static InnerClassSingleton getInstance() {
+        return SingletonHolder.instance;
+    }
+}

whatsmars-common/src/test/java/org/hongxi/java/util/lang/singleton/LazySingleton.java

+package org.hongxi.java.util.lang.singleton;
+
+/**
+ * @author shenhongxi 2019/8/11
+ */
+public class LazySingleton {
+
+    private volatile static LazySingleton instance;
+
+    private LazySingleton() {}
+
+    public static LazySingleton getInstance() {
+        if (instance == null) {
+            synchronized (LazySingleton.class) {
+                if (instance == null) {
+                    instance = new LazySingleton();
+                }
+            }
+        }
+        return instance;
+    }
+}