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Q1301. Explain Inheritance and Polymorphism.

Ans. Getting parent class object properties into child class is called Inheritance.

The process of representing one form into multiple forms is called polymorphism.

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_{Like Discuss Correct / Improve inheritance object oriented programming (oops) oops concepts polymorphism object oriented programming (oops) oops concepts Asked in 1 Companies Basic frequent}

Q1302. What is the difference between access and error log ?

Ans. We log each access to the application resource within access logs, something like

"GET / HTTP/1.0" 200 113 "-" "Mozilla/5.0 zgrab/0.x" "-"

We log only error / warn messages within error logs, something like

ERROR 123#0: *19 connect() failed

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Q1303. If Table A has 100 records and Table B has 50 records , how many records will the equi join of Table generate ?

Ans. It depends on the join condition.

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Q1304. If Table A has 100 records and Table B has 50 records , how many records will the left join of Table A with Table B generate ?

Ans. 100 records

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Q1305. If Table A has 100 records and Table B has 50 records , how many records will the right join of Table A with Table B generate ?

Ans. 50 records

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Q1306. If Table A has 0 records and Table B has 50 records , how many records will the equi join of Table generate ?

Ans. 0 records

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Q1307. What will be the output of following code

class TestMain {
public static void main(String[] args) {
String s1 = "ravi";
String s2 = new String("ravi");
Integer i = 10;
Integer a1 = new Integer("10");
System.out.println(s1 == s1);
System.out.println(i == a1);
}
}

Ans. false
false

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_{Like Discuss Correct / Improve object equality == coding code Asked in 1 Companies}

Q1308. Will the following code compile ?

final HashMap hm = new HashMap();
hm.put("Ravi", 221);

Ans. Yes, it will compile without error. final in this context means that the reference hm cannot be assigned to a new hash map but didn't restrict from changing the state of collection already held by hm.

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_{Like Discuss Correct / Improve final final variable Asked in 1 Companies}

Q1309. What is the difference between being final and being immutable ? Are string final or immutable in Java ?

Ans. Being final in the sense of objects or object reference means that the reference cannot be reassigned to a different object whereas being immutable means that the object contents cannot be changed.

Strings in Java are immutable.

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Q1310. What does the following initialization mean ?

ArrayList<LinkedList> traversalPaths = new ArrayList<LinkedList>();

What could be the use of such a collection.

Ans. Initialize an ArrayList that will hold LinkedLists i.e every element of the arraylist will be a linked list.

Such collection could be used in algorithms that require first random access and then sequential traversal. For example - Storing traversal paths for a graph wherein we can start from any vertex. Implementing dictionary with each arraylist element holding staring with character and then linked list holding duplicate words.

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_{Like Discuss Correct / Improve collections linkedlist arraylist}

Q1311. Given the list of adjacent nodes, What will be the Breadth First path

1 -> 2
1 -> 3
1 -> 6
2 -> 4
3 -> 5

Ans. 1 -> 2 -> 3 -> 6 -> 4 - > 5

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_{Like Discuss Correct / Improve breadth first traversal graph traversal}

Q1312. Given the list of adjacent nodes, What will be the Depth First path

1 -> 2
1 -> 3
1 -> 6
2 -> 4
3 -> 5

Ans. 1 -> 2 -> 4 -> 3 -> 5 -> 6

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Q1313. What will happen in a graph traversal if we don't have a check for cycle

Ans. It will result in never ending loop

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_{Like Discuss Correct / Improve graph traversal}

Q1314. What is the difference between return and continue statement ?

Ans. return is used within a method to return control out of the method. It may be followed by a value which is returned from the method to calling method immediately preceding the point of call.

continue statement is used within a loop to start next iteration without executing the remaining statements in the loop.

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_{Like Discuss Correct / Improve return statement continue statement return vs continue for loop control statements loop statement}

Q1315. What is the difference between Java SE Map and Apache Commons MultiMap ? How can we implement functionality similar to multimap using Java SE map ?

Ans. We can have duplicate keys within MultiMap whereas we cannot have duplicate keys within Java Util Map.

We can have a Map with value as a "collection of values" instead of single value to have a similar function as Multimap.

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_{Like Discuss Correct / Improve Apache commons multimap map vs multimap}

Q1316. Is it a bad practice to initialize object reference to Null ?

Ans. never initialise local to null,yes it is bad pratice

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Q1317. What will be the output of following code and Why ?

int x = 5;
int y = 7;
float f = 5f;
float z = y / x * f;
System.out.println(z);

Ans. 5.0

operation between two ints generate int only. so 7/5 generates 1 and not 1.4. Multiplication between int and float generates float and hence

1 * 5.0 = 5.0

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Q1318. Can we synchronize the run() method in Java?

^{This question is still unanswered. Can you please provide an answer.}

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Q1319. What is nested if ?

Ans. if statements nested within another if or else blocks are called nested if statements.

if(condition1) {
if(condition2){
}
}

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Q1320. what are different pointer operators used ?

^{This question was recently asked at 'Huawei Technologies'.This question is still unanswered. Can you please provide an answer.}

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Q1321. Do we have a method to reverse a string in String class ?

Ans. No but we have it in StringBuilder.

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_{Like Discuss Correct / Improve String StringBuilder Reverse a string}

Q1322. How different is it when final applied to variables and object references ?

Ans. final when assigned to object references doesn't make them immutable. It means that the references cannot be de-referenced.

final when applied to variables means that the value cannot be changed.

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Q1323. Why the following code produced this output ?

int x = 5;
int y = x;
y = 10;

System.out.println(x); // prints 5 and not 10

Ans. Because when we say y = x, the value of x is copied to another memory location and then y points to that new memory location.

Unlike object references that once assigned point to same object in memory, value is copied in case of variable assignment.

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_{Like Discuss Correct / Improve variable assignment}

Q1324. Describe how you could use a single array to implement three stacks

^{This question is still unanswered. Can you please provide an answer.}

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_{Like Discuss Correct / Improve Data Structure}

Q1325. How would you design a stack which, in addition to push and pop, also has a function min which returns the minimum element? Push, pop and min should all operate in O(1) time

^{This question is still unanswered. Can you please provide an answer.}

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Q1326. Write a program to sort a stack in ascending order You should not make any assumptions about how the stack is implemented The following are the only functions that should be used to write this program: push | pop | peek | isEmpty

^{This question is still unanswered. Can you please provide an answer.}

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_{Like Discuss Correct / Improve Data Structures}

Q1327. Explain Generics in Java ?

Ans. Generics are a facility of generic programming that were added to the Java programming language in 2004 within J2SE5.0. They allow "a type or method to operate on objects of various types while providing compile-time type safety.

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_{Like Discuss Correct / Improve generics Asked in 7 Companies}

Q1328. What are the uses of Abstraction ?

Ans. Loose Coupling
Facilitates designing complex applications by making them modular.

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Q1329. Lets say we have a set "set1" with objects of Class A, Class has a non static string called element1, Write a code ( using lambda expression ) to see if there is any object in the set with element1 = "Hello".

Ans. set1.stream().filter(p->p.element1.equals("Hello")).findAny().isPreent();

or

set1.stream().map(A::getElement1).anyMatch("Hello"::equals)

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Q1330. Which of the OOP's features facilitate dependency injection ?

Ans. Inheritance , Runtime Polymorphism and Composition.

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_{Like Discuss Correct / Improve dependency injection inversion of control ioc oops oops features}

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