26. According To Java Operator Precedence, Which Operator Is Considered To Be With Highest Precedence?
Answer: Postfix operators i.e [] . is at the highest precedence.
27. Variables Used In A Switch Statement Can Be Used With Which Data Types?
Answer: Variables used in a switch statement can only be a byte, short, int, or char.
28. When parseInt Method Can Be Used?
Answer: This method is used to get the primitive data type of a certain String.
29. Why Is String Class Considered Immutable?
Answer: The String class is immutable, so that once it is created a String object cannot be changed. Since String is immutable it can safely be shared between many threads ,which is considered very important for multithreaded programming.
30. Why Is StringBuffer Called Mutable?
Answer: The String class is considered as immutable, so that once it is created a String object cannot be changed. If there is a necessity to make a lot of modifications to Strings of characters then StringBuffer should be used.
31. What Is The Difference Between StringBuffer & StringBuilder Class?
Answer: Use StringBuilder whenever possible because it is faster than StringBuffer. But, if thread safety is necessary then use StringBuffer objects.
32. Which Package Is Used For Pattern Matching With Regular Expressions?
Answer: java.util.regex package is used for this purpose.
33. java.util.regex Consists Of Which Classes?
Answer: java.util.regex consists of three classes − Pattern class, Matcher class and PatternSyntaxException class.
34. What Is Finalize Method?
Answer: It is possible to define a method that will be called just before an object's final destruction by the garbage collector. This method is called finalize, and it can be used to ensure that an object terminates cleanly.
35. What Is An Exception?
Answer: An exception is a problem that arises during the execution of a program. Exceptions are caught by handlers positioned along the thread's method invocation stack.
36. What Do You Mean By Checked Exceptions?
Answer: It is an exception that is typically a user error or a problem that cannot be foreseen by the programmer. For example, if a file is to be opened, but the file cannot be found, an exception occurs. These exceptions cannot simply be ignored at the time of compilation.
37. Explain Runtime Exceptions?
Answer: It is an exception that occurs that probably could have been avoided by the programmer. As opposed to checked exceptions, runtime exceptions are ignored at the time of compilation.
38. Which Are The Two Subclasses Under Exception Class?
Answer: The Exception class has two main subclasses : IOException class and RuntimeException Class.
39. When throws Keyword Is Used?
Answer: If a method does not handle a checked exception, the method must declare it using the throws keyword. The throws keyword appears at the end of a method's signature.
40. When throw Keyword Is Used?
Answer: An exception can be thrown, either a newly instantiated one or an exception that you just caught, by using throw keyword.
41. How finally Keyword Is Used Under Exception Handling?
Answer: The finally keyword is used to create a block of code that follows a try block. A finally block of code always executes, whether or not an exception has occurred.
42. What Things Should Be Kept In Mind While Creating Your Own Exceptions In Java?
Answer: While creating your own exception,
43. Define Inheritance?
Answer: It is the process where one object acquires the properties of another. With the use of inheritance the information is made manageable in a hierarchical order.
44. When super Keyword Is Used?
Answer: If the method overrides one of its superclass's methods, overridden method can be invoked through the use of the keyword super. It can be also used to refer to a hidden field.
45. What Is Polymorphism?
Answer: Polymorphism is the ability of an object to take on many forms. The most common use of
polymorphism in OOP occurs when a parent class reference is used to refer to a child class object.
46. What Is Abstraction?
Answer: It refers to the ability to make a class abstract in OOP. It helps to reduce the complexity and also improves the maintainability of the system.
47. What Is Abstract Class?
Answer: These classes cannot be instantiated and are either partially implemented or not at all implemented. This class contains one or more abstract methods which are simply method declarations without a body.
48. When Abstract Methods Are Used?
Answer: If you want a class to contain a particular method but you want the actual implementation of that method to be determined by child classes, you can declare the method in the parent class as abstract.
49. What Is Encapsulation?
Answer: It is the technique of making the fields in a class private and providing access to the fields via public methods. If a field is declared private, it cannot be accessed by anyone outside the class, thereby hiding the fields within the class. Therefore encapsulation is also referred to as data hiding.
50. What Is The Primary Benefit Of Encapsulation?
Answer: The main benefit of encapsulation is the ability to modify our implemented code without breaking the code of others who use our code. With this Encapsulation gives maintainability, flexibility and extensibility to our code.
Check Out Other Questions As Well: -
51. What Is An Interface?
52. Give Some Features Of Interface?
53. Define Packages In Java?
54. Why Packages Are Used?
55. What Do You Mean By Multithreaded Program?
56. What Are The Two Ways In Which Thread Can Be Created?
57. What As An Applet? An Applet Extends Which Class?
58. Explain Garbage Collection In Java?
59. Define Immutable Object?
60. Explain The Usage Of This With Constructors?
61. Explain Set Interface?
62. Explain TreeSet?
63. What Is Comparable Interface?
64. Difference Between Throw & Throws?
65. Explain The Following Line Used Under Java Program − public static void main Stringargs[]
66. Define JRE i.e. Java Runtime Environment?
67. What Is JAR File?
68. What Is A WAR File?
69. Define JIT Compiler?
70. What Is The Difference Between Object Oriented Programming Language & Object Based Programming Language?
71. What Is The Purpose Of Default Constructor?
72. Can A Constructor Be Made Final?
73. What Is Static Block?
74. Define Composition?
75. What Is Function Overloading?
...Return To Java FAQ's Section
Answer: Postfix operators i.e [] . is at the highest precedence.
27. Variables Used In A Switch Statement Can Be Used With Which Data Types?
Answer: Variables used in a switch statement can only be a byte, short, int, or char.
28. When parseInt Method Can Be Used?
Answer: This method is used to get the primitive data type of a certain String.
29. Why Is String Class Considered Immutable?
Answer: The String class is immutable, so that once it is created a String object cannot be changed. Since String is immutable it can safely be shared between many threads ,which is considered very important for multithreaded programming.
30. Why Is StringBuffer Called Mutable?
Answer: The String class is considered as immutable, so that once it is created a String object cannot be changed. If there is a necessity to make a lot of modifications to Strings of characters then StringBuffer should be used.
31. What Is The Difference Between StringBuffer & StringBuilder Class?
Answer: Use StringBuilder whenever possible because it is faster than StringBuffer. But, if thread safety is necessary then use StringBuffer objects.
32. Which Package Is Used For Pattern Matching With Regular Expressions?
Answer: java.util.regex package is used for this purpose.
33. java.util.regex Consists Of Which Classes?
Answer: java.util.regex consists of three classes − Pattern class, Matcher class and PatternSyntaxException class.
34. What Is Finalize Method?
Answer: It is possible to define a method that will be called just before an object's final destruction by the garbage collector. This method is called finalize, and it can be used to ensure that an object terminates cleanly.
35. What Is An Exception?
Answer: An exception is a problem that arises during the execution of a program. Exceptions are caught by handlers positioned along the thread's method invocation stack.
36. What Do You Mean By Checked Exceptions?
Answer: It is an exception that is typically a user error or a problem that cannot be foreseen by the programmer. For example, if a file is to be opened, but the file cannot be found, an exception occurs. These exceptions cannot simply be ignored at the time of compilation.
37. Explain Runtime Exceptions?
Answer: It is an exception that occurs that probably could have been avoided by the programmer. As opposed to checked exceptions, runtime exceptions are ignored at the time of compilation.
38. Which Are The Two Subclasses Under Exception Class?
Answer: The Exception class has two main subclasses : IOException class and RuntimeException Class.
39. When throws Keyword Is Used?
Answer: If a method does not handle a checked exception, the method must declare it using the throws keyword. The throws keyword appears at the end of a method's signature.
40. When throw Keyword Is Used?
Answer: An exception can be thrown, either a newly instantiated one or an exception that you just caught, by using throw keyword.
41. How finally Keyword Is Used Under Exception Handling?
Answer: The finally keyword is used to create a block of code that follows a try block. A finally block of code always executes, whether or not an exception has occurred.
42. What Things Should Be Kept In Mind While Creating Your Own Exceptions In Java?
Answer: While creating your own exception,
- All exceptions must be a child of Throwable.
- If you want to write a checked exception that is automatically enforced by the Handle or
- Declare Rule, you need to extend the Exception class.
- You want to write a runtime exception, you need to extend the RuntimeException class.
43. Define Inheritance?
Answer: It is the process where one object acquires the properties of another. With the use of inheritance the information is made manageable in a hierarchical order.
44. When super Keyword Is Used?
Answer: If the method overrides one of its superclass's methods, overridden method can be invoked through the use of the keyword super. It can be also used to refer to a hidden field.
45. What Is Polymorphism?
Answer: Polymorphism is the ability of an object to take on many forms. The most common use of
polymorphism in OOP occurs when a parent class reference is used to refer to a child class object.
46. What Is Abstraction?
Answer: It refers to the ability to make a class abstract in OOP. It helps to reduce the complexity and also improves the maintainability of the system.
47. What Is Abstract Class?
Answer: These classes cannot be instantiated and are either partially implemented or not at all implemented. This class contains one or more abstract methods which are simply method declarations without a body.
48. When Abstract Methods Are Used?
Answer: If you want a class to contain a particular method but you want the actual implementation of that method to be determined by child classes, you can declare the method in the parent class as abstract.
49. What Is Encapsulation?
Answer: It is the technique of making the fields in a class private and providing access to the fields via public methods. If a field is declared private, it cannot be accessed by anyone outside the class, thereby hiding the fields within the class. Therefore encapsulation is also referred to as data hiding.
50. What Is The Primary Benefit Of Encapsulation?
Answer: The main benefit of encapsulation is the ability to modify our implemented code without breaking the code of others who use our code. With this Encapsulation gives maintainability, flexibility and extensibility to our code.
Check Out Other Questions As Well: -
51. What Is An Interface?
52. Give Some Features Of Interface?
53. Define Packages In Java?
54. Why Packages Are Used?
55. What Do You Mean By Multithreaded Program?
56. What Are The Two Ways In Which Thread Can Be Created?
57. What As An Applet? An Applet Extends Which Class?
58. Explain Garbage Collection In Java?
59. Define Immutable Object?
60. Explain The Usage Of This With Constructors?
61. Explain Set Interface?
62. Explain TreeSet?
63. What Is Comparable Interface?
64. Difference Between Throw & Throws?
65. Explain The Following Line Used Under Java Program − public static void main Stringargs[]
66. Define JRE i.e. Java Runtime Environment?
67. What Is JAR File?
68. What Is A WAR File?
69. Define JIT Compiler?
70. What Is The Difference Between Object Oriented Programming Language & Object Based Programming Language?
71. What Is The Purpose Of Default Constructor?
72. Can A Constructor Be Made Final?
73. What Is Static Block?
74. Define Composition?
75. What Is Function Overloading?
...Return To Java FAQ's Section
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