Java Questions 51 - 100  «Prev Next»

Array, ArrayList (Interview Questions)

  1. How can you compare arrays for equality?

    Answer:
    You can compare arrays for equality with the convenience method Java.util.Arrays.equals()

  2. What is the purpose of cloning in object-oriented programming?

    Answer:
    The purpose of cloning is to create an independent copy of an object.

  3. What must you do to create a "deep copy" in Java?

    Answer:
    To make a deep copy you must create cloned copies of all components (excluding Strings and primitive values) by invoking their respective clone methods.

  4. What type of Exception class is CloneNotSupportedException?

    Answer:
    It is a checked exception class.

  5. What are two different ways to view an array?

    Answer:
    1. You can view it as a collection of individual indexed variables like
    temp[0],..., temp[n]
    
    2. You can view an array as one large composite object that has a number of different values all of the same type

  6. What is the difference between String and Stringbuffer?

    Answer:
    The String Buffer class represents a mutable string of characters that can grow or shrink as necessary. Its mutability makes it suitable for processing text in place which is not possible with the immutable String class.

  7. What does "protected" visibility for 1) fields and 2) methods allow?

    Answer:
    Because it is fairly common for a subclass method to reference data fields in its superclass, Java provides a less restrictive form of visibility called protected visibility. A data field (or method) with protected visibility can be accessed in either the class defining it, in any subclass of that class, or any class in the same package.

  8. When would you advise to use an ArrayList?

    Answer:
    ArrayList objects are used most often when a programmer wants to be able to add new elements to the end of a list but still needs the capability to access the elements stored in the list in arbitrary order. The ArrayList class implements a growable array of objects.

  9. What is IllegalMonitorStateException?

    Answer:
    This signals an illegal monitor state. It is thrown by the Object notify() and wait() methods used for thread synchronization.

  10. What is the advantage of "ArrayList" over Vector?

    Answer: ArrayList is like Vector without the synchronization overhead.
    Vector and Stack are legacy implementations left over from Java 1.0