Core Java Interview Questions, Answers for Freshers and Experienced asked in various Company Job Interviews

Core Java Interview Questions

Questions Answers Views Company eMail

Is it possible to write JAVA program without including any of the packages,such as "import java.io.*"; bcoz I instantly wrote a code without "import..." statement and runned the program on command Line & it worked. the code is: class Person { String name; int age; Person(String s,int a) { name = s; age = a; } accept() { System.out.println(name+"Hi!!!!!"); System.out.println(age); } } class Demo { public static void main(Strings args[])throws IOException { String name = args[0]; int age = Integer.parseInt(args[1]); Person p = new Person(name,age); p.accept(); } }

3 4814

1) There are 10 different threads in runnable state. Each having priority 1 to 10. How does the CPU schedules or executes these threads?

RBS,

2 6627

2) Suppose there are 5 directories having lot of files (say txt files) in each directory. 2 things :- 2.1) You want to search for filenames which have a particular pattern. 2.2) Out of these filtered files you want to search for a particular keyword or a search string. How can you achieve this?

RBS, TCS,

2106

3) Suppose you are a very rich person, having 50 rooms and you have lost the key for one of the room's. How effectively you can find this key? (Qs2 and Qs3 are related)

RBS,

3 8393

Suppose there is a System A which gives some output. This output is used as input by system B. The rate at which System A produces is faster than the rate at which system B consumes it. How can you improve this?

RBS,

1 5451

Suppose there is an Online shopping cart application having different objects like Cart, SelectionItem, Billing, COnfiguration, Authentication, Authorization, PersonalDetails etc. Out of this which one can be made a singleton pattern and why?

RBS,

2 10310

What is Co-Variant return type in method overriding?

RBS,

1 5459

7) Suppose there is Student class like class student { int age; string name; } We want to store these objects in a HashMap. Do we need to override any methods in Student class? If any which ones and why? what if i just override equals or just hashcode? what will be the results in both the cases?

CSC, Nagarro, RBS,

4 8454

Can an abstract class have a constructor?

RBS, Wipro,

1 9266

What is the life cycle of Servlet?

3 5917

JVM responsibility?

TCS,

6 15320

explain Anonynous inner class?

TCS,

6 8746

why is S capital in System.out.println ????

6 19636

what is difference between length and length()?

8 16926

how your day start in your company

1 3454

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Un-Answered Questions { Core Java }

What is jit and its use?

826

Is array size fixed in java?

780

What are the restrictions imposed on method overriding?

818

Can we declare a static variable inside a method?

781

Can we change the value of static variable?

751

What are strings in physics?

810

What are peerless components in java programming?

815

What are synchronized methods and synchronized statements in java programming?

829

What is java virtual machine? Explain

806

can java object be locked down for exclusive use by a given thread? : Java thread

828

Does every java program need a main?

807

what is the purpose of "virtual"?

843

What is the major advantage of external iteration over internal iteration?

864

When does a class need a virtual destructor?

787

What are the data types supported by java?

800

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