add demo for how memory is allocated in java

src/main/java/jvm/gc/PrintMemoryAddress.java

@@ -0,0 +1,21 @@
+package jvm.gc;
+
+public class PrintMemoryAddress {
+    public Object getObj() {
+        Object o = new Object();
+        System.out.println(STR."The addree is \{System.identityHashCode(o)}");
+        return o;
+    }
+
+    public void showObj() {
+        Object o = getObj();
+        Object o2 = new Object();
+        System.out.println(STR."Now the addree is \{System.identityHashCode(o)}");
+        System.out.println(STR."The addree of o2 is \{System.identityHashCode(o2)}");
+    }
+
+    public static void main(String[] args) {
+        PrintMemoryAddress printMemoryAddress = new PrintMemoryAddress();
+        printMemoryAddress.showObj();
+    }
+}