add testcase & remove unused code

src/test/java/com/alibaba/druid/bvt/utils/ConcurrentIdentityHashMapTest3.java

@@ -0,0 +1,39 @@
+package com.alibaba.druid.bvt.utils;
+
+import java.util.Map;
+
+import junit.framework.TestCase;
+
+import org.junit.Assert;
+
+import com.alibaba.druid.util.ConcurrentIdentityHashMap;
+
+public class ConcurrentIdentityHashMapTest3 extends TestCase {
+
+    public void test_0() throws Exception {
+        ConcurrentIdentityHashMap<Integer, Object> map = new ConcurrentIdentityHashMap<Integer, Object>(16, 0.75f, 2);
+
+        Integer[] keys = new Integer[10000];
+        for (int i = 0; i < keys.length; ++i) {
+            keys[i] = i;
+        }
+        for (int i = 0; i < keys.length; ++i) {
+            map.put(keys[i], "");
+        }
+        Assert.assertEquals(keys.length, map.size());
+        for (int i = 0; i < keys.length; ++i) {
+            map.put(keys[i], "");
+        }
+        for (Map.Entry<Integer, Object> entry : map.entrySet()) {
+            entry.getKey();
+            entry.getValue();
+        }
+        Assert.assertEquals(keys.length, map.size());
+        for (int i = 0; i < keys.length; ++i) {
+            map.remove(keys[i]);
+        }
+        Assert.assertEquals(0, map.size());
+        map.keys();
+        map.entrySet();
+    }
+}