From 63473ed3e19a9d7f985de7c3d0f5bc675d75c23e Mon Sep 17 00:00:00 2001
From: YuCheng Hu <yuchenghu@ossez.com>
Date: Wed, 21 Nov 2018 14:49:21 -0500
Subject: [PATCH] =?UTF-8?q?Java=20=E8=AE=BE=E8=AE=A1=E6=A8=A1=E5=BC=8F?=
 =?UTF-8?q?=E4=B8=AD=E7=9A=84=E5=8D=95=E4=BE=8B=E6=A8=A1=E5=BC=8F?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../lang/tutorial/tests/SingletonTest.java    | 69 +++++++++++++++++++
 1 file changed, 69 insertions(+)
 create mode 100644 src/test/java/com/ossez/lang/tutorial/tests/SingletonTest.java

diff --git a/src/test/java/com/ossez/lang/tutorial/tests/SingletonTest.java b/src/test/java/com/ossez/lang/tutorial/tests/SingletonTest.java
new file mode 100644
index 0000000000..a6cd888777
--- /dev/null
+++ b/src/test/java/com/ossez/lang/tutorial/tests/SingletonTest.java
@@ -0,0 +1,69 @@
+package com.ossez.lang.tutorial.tests;
+
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Eager Singleton
+ * 
+ * @author YuCheng
+ *
+ */
+class EagerSingleton {
+	private static final EagerSingleton INSTANCE = new EagerSingleton();
+
+	// Private constructor suppresses
+	private EagerSingleton() {
+	}
+
+	// default public constructor
+	public static EagerSingleton getInstance() {
+		return INSTANCE;
+	}
+}
+
+/**
+ * Lazy Singleton
+ * 
+ * @author YuCheng
+ *
+ */
+class LazySingleton {
+	private static volatile LazySingleton INSTANCE = null;
+
+	// Private constructor suppresses
+	// default LazySingleton constructor
+	private LazySingleton() {
+	}
+
+	// thread safe and performance promote
+	public static LazySingleton getInstance() {
+		if (INSTANCE == null) {
+			synchronized (LazySingleton.class) {
+				// when more than two threads run into the first null check same time, to avoid instanced more than one time, it needs to be
+				// checked again.
+				if (INSTANCE == null) {
+					INSTANCE = new LazySingleton();
+				}
+			}
+		}
+		return INSTANCE;
+	}
+}
+
+/**
+ * 
+ * @author YuCheng
+ *
+ */
+public class SingletonTest {
+	private final static Logger logger = LoggerFactory.getLogger(SingletonTest.class);
+
+	@Test
+	public void testSingleton() {
+		logger.debug("TEST Singleton");
+
+	}
+
+}