Java Interview Questions 14

66: What one should take care of while serializing the object?
A: One should make sure that all the included objects are also serializable. If any of the objects is not serializable then it throws a NotSerializableException.

67: What happens to the static fields of a class during serialization?
A: There are three exceptions in which serialization doesnot necessarily read and write to the stream. These are
1. Serialization ignores static fields, because they are not part of ay particular state state.
2. Base class fields are only hendled if the base class itself is serializable.
3. Transient fields

68: Does Java provide any construct to find out the size of an object?
A: No there is not sizeof operator in Java. So there is not direct way to determine the size of an object directly in Java.

69: Does importing a package imports the subpackages as well? e.g. Does importing com.MyTest.* also import com.MyTest.UnitTests.*?
A: Read the system time just before the method is invoked and immediately after method returns. Take the time difference, which will give you the time taken by a method for execution.
To put it in code...
long start = System.currentTimeMillis ();
method ();
long end = System.currentTimeMillis ();
System.out.println ("Time taken for execution is " + (end - start));
Remember that if the time taken for execution is too small, it might show that it is taking zero milliseconds for execution. Try it on a method which is big enough, in the sense the one which is doing considerable amout of processing.

70: What are wrapper classes?
A: Java provides specialized classes corresponding to each of the primitive data types. These are called wrapper classes. They are e.g. Integer, Character, Double etc.