Core Java - Interview Questions and Answers for 'Core Java' | Search Interview Question

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Q1181. Difference between HashMap and Dictionary in Java ?

Ans. HashMap implements the Map interface while the Dictionary does not.

HashMap was introduced after HashTable and Dictionary.

Dictionary is currently obsolete in java.

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Q1182. Difference between System.getEnv and System.getProperties ?

Core Java

Ans. System.getEnv gets the environment variables where System.getProperties gets Java properties.

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Q1183. Can we load environment variables into Properties in Java ? How ?

Core Java

Ans. Yes

new Properties().putAll(System.getenv());

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Q1184. Can we have two interfaces having method with same name and arguments?

Core Java

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Q1185. how hashmap work? Write a program that uses map interface ?

Core Java

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Q1186. If we have a return statement inside the finally block, Then what will happen ?

Core Java

Ans. Returning from inside a finally block will cause exceptions to be lost. A return statement inside a finally block will cause any exception that might be thrown in the try block to be discarded.

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Q1187. Can we have more than two constructors in a class ?

Core Java

Ans. Yes, through constructor overloading

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Q1188. What is something faulty about java ?

Core Java

Ans. Not purely object oriented Language.

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Q1189. What are meta classes in Java ?

Core Java

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Q1190. Have you ever faced any problem because of PrintWriter buffer and autoflush mechanism ? How did you got rid of it ?

Core Java

Ans. Yes , we faced trouble once wherein we were trying to set certain elements to the PrintWriter. As in some cases the PrintWriter held too much information and hence it would get flushed before we could append those elements.

We disabled auto flushing and provided our own explicit flushing.

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Q1191. Can we disable auto flushing for PrintWriter ?

Core Java

Ans. Yes

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Q1192. Can we increase the buffer size while working with Buffered Streams ? How ?

Core Java

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Q1193. What are the 22 possible values of x where x== -x (true) ?

Core Java

Ans. byte x = 0;
short x = 0;
char x = 0;
int x = 0;
int x = Integer.MIN_VALUE;
float x = 0.0f;
float x = -0.0f;
long x = 0;
long x = Long.MIN_VALUE;
double x = 0.0;
double x = -0.0;
Byte x = 0;
Short x = 0;
Character x = 0;
Integer x = 0;
Integer x = Integer.MIN_VALUE;
Float x = 0.0f;
Float x = -0.0f;
Long x = 0L;
Long x = Long.MIN_VALUE;
Double x = 0.0;
Double x = -0.0;

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Q1194. Combine and join integer and string list to single list and sort.

Core Java

Ans. Object[] combined = new Object[first.length second.length];
System.arraycopy(first, 0, combined, 0, first.length);
System.arraycopy(second, 0, combined, first.length, second.length);

-- OR --

Object[] combined = Stream.concat(Arrays.stream(first), Arrays.stream(second)).toArray();

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Q1195. Difference between interface and inheritance

Core Java

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Q1196. Write program to recursively iterate through map ?

Core Java

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Q1197. Can you give me a use case where you utilized serialization in your project code?

Core Java

Ans. we use serialization when we send response to client in JSON format.(the process of converting model object into json is nothing but serialization

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Q1198. Which interface is used for hashset implementation ?

Core Java

Ans. HashSet implements Set interface.

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Q1199. Difference between function overloading and method overloading?

Core Java

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Q1200. Which is faster, LinkedList or ArrayList?

Core Java

Ans. ArrayList is fast for random access, but is slow on deletion and insertion.

LinkedList is slow for random access, but is fast on deletion and insertion.

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Q1201. Write an algorithm for square root of a given number.

Core Java

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Q1202. What is meant by platform ? Which platform does java provides ?

Core Java

Ans. platform is the hardware or software environment in which a program runs. There are two types of platforms software-based and hardware-based. Java provides software-based platform.

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Q1203. Why packages are used in Java ?

Core Java

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Q1204. Is it possible to have a static class ?

Core Java

Ans. We can have a static inner class but not static outer class.

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Q1205. Why in Java does it require "static" in the main function?

Core Java

Ans. Because there needs to be a starting point till when there is no object created in memory and hence it needs to be run in static scope

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Q1206. What are the different types of inheritance ?

Core Java

Ans. Single Level
Multi Level
Hierarchical
Multiple
Hybrid

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Q1207. Is there a way to access a private method from an outside class ?

Core Java

Ans. Through Reflection.

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Q1208. Difference between class and object with example.

Core Java

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Q1209. What if we use all access specifiers ? Is it encapsulation ?

Core Java

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Q1210. Explain how a class is loaded ?

Core Java

Ans. Java classLoder is resposible to load java classes.

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