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Showing posts with label Java Interview QA. Show all posts
Showing posts with label Java Interview QA. Show all posts

Java Map Comparison- hashmap, linkedhashmap, treemap

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Java Map Comparison : HashMap is the fastest map with O(1) search and insertion times. LinkedHashMap is a little slower for inserts, bu...

Java iterate through map, hashmap - working source code

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Iterating through Map in Java - working efficient source code  Map<String, Object> map = ...; The solution uses map.keySet(), map....

Top Java Interview Question : reverse a string using recursion

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Best Answer using Recursion : public String reverse(String str) { if ((null == str) || (str.length() <= 1)) { return st...

Call one constructor from another in Java

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Is this possible to call one constructor from another in Java ? Yes, it is possible: public class Foo { private int x; public F...

Scenarios in which Serialization cannot happen

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What are the special cases in which serialization cannot happen? -> There are following scenarios in which serialization cannot happen: a...

redirect message to IO stream

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How could Java classes direct program messages to the system console, but error messages, say to a file? The class System has a variable ou...

How to serialize variables selectively

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In a Java class, one has 10 variables. One wants to serialize only 3 variables,how can this be achieved? ->Make variables as ' trans...

The usage of Java packages.

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Explain the usage of Java packages. A. This is a way to organize files when a project consists of multiple modules. It also helps resol...

Java: difference between private, protected, and public?

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These keywords are for allowing privileges to components such as java methods and variables. Public : accessible to all classes Private : ...

Order of catching exception in java

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Does it matter in what order catch statements for FileNotFoundException and IOExceptipon are written? A. Yes, it does. The FileNotFoundEx...

wrapper classes in Java

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Describe the wrapper classes in Java. Wrapper class is wrapper around a primitive data type. An instance of a wrapper class contains, or wra...

Java Class as Applet as well as Application

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Can you write a Java class that could be used both as an applet as well as an application? A. Yes. Add a main() method to the applet.

Redirect Standard System Output and Error Message to PrintStream in Java

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In a Java program, how can you divert standard system output or error messages, say to a file? ->We can achieve this by using public st...

difference between an interface and an abstract class

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What's the difference between an interface and an abstract class? Also discuss the similarities.  (Very Important) Abstract class is a ...