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

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Q1081. Where are arrays stored in memory - stack or heap ?

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Q1082. Are Arrays treated like primitives or like objects in Java ?

Core Java

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Q1083. How can we check equality for Arrays in Java ?

Core Java

Ans. You call the method java.util.Arrays.equals(Object[] a, Object[] a2)?

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Q1084. Are arrays Thread Safe ?

Core Java

Ans. Yes

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Q1085. What is the time and space complexity for different operations for arrays ?

Core Java

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Q1086. Write code to serialize and deserialize an array of strings ?

Core Java

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Q1087. Can we have 3 dimensional arrays in Java ?

Core Java

Ans. Yes

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Q1088. Can we make array volatile in Java ?

Core Java

Ans. Yes, you can make an array (both primitive and reference type array e.g. an int array and String array) volatile in Java but only changes to reference pointing to an array will be visible to all threads, not the whole array

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Q1089. How do you implement 'state and behavior' of object in Java program?

Core Java

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Q1090. How is it possible to use concat on string objects in Java, based on the fact that string is immutable?

Core Java

Ans. It's possible because internally java first reserves the memory for the new concatenated string and then copy that over. So after concatenation, there are 2 strings in memory, the original one and the concatenated one and then the reference is moved to the concatenated string.

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Q1091. Difference between static and dynamic memory allocation ?

Core Java

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Q1092. Why Arrays are considered as data structures whereas ArrayList isn't ?

Core Java

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Q1093. Are Arrays a data structure or a collection class ?

Core Java

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Q1094. Which Java version supports Interface Default methods ?

Core Java

Ans. Java 1.8 or Java 8

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Q1095. Tell something about Sleep method.

Core Java

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Q1096. Diff between Runtime.getRunTime().gc() and System.gc()

Core Java

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Q1097. How to run jar file using command prompt

Core Java

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Q1098. Can we call a static method using reference currently pointing to null.

Core Java

Ans. yes, we can.
exa: public class Java{
public static void main(String... args) {
JAva j= null;
j.greeting(); // call with null reference
}
public static void greeting() {
System.out.println("Hello World");
}
} // output: Hello World

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Q1099. Which memory segment holds the byte code ?

Core Java

Ans. Code Segment

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Q1100. Is this array declaration correct ? If not , Why ?

String[] strArray = new String[];

Core Java

Ans. No, We haven't specified the size of array to be initialized.

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Q1101. Is this array initialization correct ? If Yes, What will be the size of array ?

String[] strArray = new String[]{"Buggy","Bread"};

Core Java

Ans. Yes, size of the array will be 2.

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Q1102. Is this array initialization correct ? If Yes, What will be the size of array ?

String[] strArray = new String[3]{"Buggy","Bread"};

Core Java

Ans. No. It will result in error saying "Cannot define dimension expressions when an array initializer is provided"

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Q1103. Is this code valid

String[] strArray = new String[2];
strArray.length = 5;

Core Java

Ans. It will give compile time error saying "The final field array.length cannot be assigned"

Arrays once initialized cannot be resized.

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Q1104. What is the problem with this code

String[] strArray = new String[2];
strArray[0] = 5;

Core Java

Ans. We are trying to add an integer element to an array of String. Will give compile time error.

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Q1105. Will this give compile time error ?

Object[] strArray = new String[2];
strArray[0] = 5;

Core Java

Ans. No. But It will throw ArrayStoreException at runtime.

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Q1106. What is TypeCasting ?

Core Java

Ans. Assigning a value of one type to a variable of another type is known as Type Casting.

Example :

int x = 10;
byte y = (byte)x;

In Java, type casting is classified into two types, Widening Casting(Implicit) widening-type-conversion and Narrowing Casting (Explicitly done) narrowing-type-conversion.

Widening or Automatic type converion - Automatic Type casting take place when,the two types are compatible and the target type is larger than the source type

Example :

public class Test {
public static void main(String[] args) {
int i = 100;
long l = i; //no explicit type casting required
float f = l;//no explicit type casting required
System.out.println("Int value " i);
System.out.println("Long value " l);
System.out.println("Float value " f);
}
}

Narrowing or Explicit type conversion - When you are assigning a larger type value to a variable of smaller type, then you need to perform explicit type casting.

Example :

public class Test{
public static void main(String[] args) {
double d = 100.04;
long l = (long)d; //explicit type casting required
int i = (int)l;//explicit type casting required
System.out.println("Double value " d);
System.out.println("Long value " l);
System.out.println("Int value " i);
}
}

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Q1107. What is the biggest Design problem in Java ?

Core Java

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Q1108. Write a java program to find the maximum profit in day trading

Core Java

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Q1109. What are basic functions of OOPS ?

Core Java

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Q1110. Where to use interface and abstract class ?

Core Java

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