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

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Q1171. Difference between composition and aggregation in java ?

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Q1172. Does garbage collection affects performance of the application ?

Core Java

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Q1173. Does garbage collection happens in String pool ?

Core Java

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Q1174. Does garbage collection call dispose ?

Core Java

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Q1175. What is the difference between final and static in java ?

Core Java

Ans. final keyword is used to restrict the user from modifying the variable, extending the class and overriding a method

static keyword is used for memory management which can be used for variable, class, method where in it belongs to the class not to the instance of object

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Q1176. How can we run a java program through command line ?

Core Java

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Q1177. Difference between ArrayList and Vector ?

Core Java

Ans. Vector is Synchronized one where as Arraylist is not Synchronized.

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Q1178. difference between ArrayList and array ?

Core Java

Ans. ArrayList is a variable length collection class whereas arrays are fixed length primitive structure.

We can use generics with arraylist but not with arrays.

We can store primitive data types within arrays but can't with ArrayList. In ArrayList that needs to be converted to Wrapper objects.

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Q1179. Difference between ArrayList and HashSet ?

Core Java

Ans. ArrayList is a list , i.e an implementation of List interface whereas HashSet is a Set and an implementation of Set interface.

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Q1180. Difference between TreeMap and SortedMap ?

Core Java

Ans. sortedMap is an interface ,while TreeMap is an implementation of sortMap.

We can not create an instance of sortedMap but we can create an instance of treeMap

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Q1181. Difference between HashMap and Dictionary in Java ?

Core 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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