diff --git a/src/main/java/jvm/gc/MemoryAllocationYoung.java b/src/main/java/jvm/gc/MemoryAllocationYoung.java
new file mode 100644
index 0000000..201e10e
--- /dev/null
+++ b/src/main/java/jvm/gc/MemoryAllocationYoung.java
@@ -0,0 +1,24 @@
+package jvm.gc;
+
+/**
+ * VM Args: -verbose:gc -Xmx20M -Xms20M -Xmn10M -Xlog:gc* -XX:SurvivorRatio=8
+ * new objects by default will go to eden first, when eden has no enough space,
+ * it will trigger minor gc, and move objects from eden to old generation.
+ */
+public class MemoryAllocationYoung {
+    private static final int _1MB = 1024 * 1024;
+
+    public static void  testAllocation() {
+        byte[] a,b,c,d;
+        a = new byte[2 * _1MB];
+        b = new byte[2 * _1MB];
+        c = new byte[2 * _1MB];
+        d = new byte[4 * _1MB];
+
+    }
+
+    public static void main(String[] args) {
+        testAllocation();
+    }
+
+}
diff --git a/src/main/java/jvm/gc/TenuringThreshold.java b/src/main/java/jvm/gc/TenuringThreshold.java
new file mode 100644
index 0000000..8e12650
--- /dev/null
+++ b/src/main/java/jvm/gc/TenuringThreshold.java
@@ -0,0 +1,24 @@
+package jvm.gc;
+
+/**
+ * VM Args: -verbose:gc -Xmx20M -Xms20M -Xmn10M -Xlog:gc+age=trace -XX:SurvivorRatio=8 -XX:MaxTenuringThreshold=1
+ * -verbose:gc -Xmx20M -Xms20M -Xmn10M -Xlog:gc+age=trace -XX:SurvivorRatio=8 -XX:MaxTenuringThreshold=15
+ */
+@SuppressWarnings("unused")
+public class TenuringThreshold {
+    public static final int _1MB = 1024 * 1024;
+
+    public static void testTenuringThreshold() {
+        byte[] allocation1, allocation2, allocation3;
+
+        allocation1 = new byte[_1MB / 4];
+        allocation2 = new byte[4 * _1MB];
+        allocation3 = new byte[4 * _1MB];
+        allocation3 = null;
+        allocation3 = new byte[4 * _1MB];
+    }
+
+    public static void main(String[] args) {
+        testTenuringThreshold();
+    }
+}