reuse bytebuffer

other/java/client/src/main/java/seaweedfs/client/ByteBufferPool.java

@@ -0,0 +1,22 @@
+package seaweedfs.client;
+
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.List;
+
+public class ByteBufferPool {
+
+    static List<ByteBuffer> bufferList = new ArrayList<>();
+
+    public static synchronized ByteBuffer request(int bufferSize) {
+        if (bufferList.isEmpty()) {
+            return ByteBuffer.allocate(bufferSize);
+        }
+        return bufferList.remove(bufferList.size()-1);
+    }
+
+    public static synchronized void release(ByteBuffer obj) {
+        bufferList.add(obj);
+    }
+
+}