Java Virtual Machine - Memory Leak in Java

We shall discuss about the memory leak concept in Java in this chapter.

The following code creates a memory leak in Java −

void queryDB() {
   try{
      Connection conn = ConnectionFactory.getConnection();
      PreparedStatement ps = conn.preparedStatement("query"); // executes a
      SQL
      ResultSet rs = ps.executeQuery();
      while(rs.hasNext()) {
         //process the record
      }
   } catch(SQLException sqlEx) {
      //print stack trace
   }
}

In the above code, when the method exits, we have not closed the connection object. Thus, the physical connection remains open before the GC is triggered and sees the connection object as unreachable. Now, it will call the final method on the connection object, however, it may not be implemented. Hence, the object will not be garbage collected in this cycle.

The same thing will happen in the next until the remote server sees that the connection has been open for a long time and forcefully terminates it. Thus, an object with no reference remains in the memory for a long time which creates a leak.