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Q1411. Write code to print a Pyramid pattern ?

Ans. public static void printTriagle(int n)
{
// outer loop to handle number of rows
// n in this case
for (int i=0; i1; j--)
{
// printing spaces
System.out.print(" ");
}

// inner loop to handle number of columns
// values changing acc. to outer loop
for (int j=0; j<=i; j )
{
// printing stars
System.out.print("* ");
}

// ending line after each row
System.out.println();
}
}

// Driver Function
public static void main(String args[])
{
int n = 5;
printTriagle(n);
}

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Q1412. What does System.exit() do ?

Ans. Generally used to indicate termination

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Q1413. How to sort objects based on one of the field ?

Ans. Using comparable and comparator and sorted collections like TreeSet or TreeMap.

or

use stream api from java 8 onwards which internally refers to comparable and comparator through lambda expressions

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Q1414. Can we have interface as a replacement for utility class ?

Ans. Yes, With Java 8 we can use Interfaces as collection of utility methods through the use of default methods.

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Q1415. What are custom annotations and How can we create one ?

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Q1416. What is the difference between scope and access modifiers ?

Ans. Scope modifiers changes the scope of a particular element or a method. For ex - static changes the scope of that of class and not of object.

Access modifiers changes the access priviledges of a particular element or a method. For ex - private , public etc.

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Q1417. Why Java has final class ?

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Q1418. Which memory segment is cleaned by Garbage Collection - stack or heap ?

Ans. Heap as objects are stored ink heap.

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Q1419. Do we have references for the objects that are eligible for garbage collection ?

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Q1420. Are final methods faster than regular instance methods ?

Ans. Yes. As they cannot be overridden , there is no use of virtual table concept which is used for dynamic binding resolution.

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Q1421. What is virtual table with respect to method overriding in Java ?

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Q1422. How is the virtual method table implemented in Java?

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Q1423. How many VTables are there for each class ?

Ans. There is one VTable for each class.

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Q1424. Have you ever used java.util.Objects class ?

Ans. Yes, We are using requireNonNull method for validating if the object is null.

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Q1425. Why do we use getbytes in Java?

Ans. It is used to convert String into an array of bytes.

byte[] getBytes() - converts String into a byte array.

byte[] getBytes(Charset charset) - converts String to byte array, based on charset encoding.

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Q1426. Can Java be run on hardware with just the JVM and no OS ?

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Q1427. Which java feature is used to convert primitive type to reference type ?

Ans. AutoBoxing

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Q1428. What is a reflexive equals contract ?

Ans. An equal contract is said to be reflexive is equality between 2 objects always returns to be true.

For example -

Object o1;
Object o2;

o1.equals(o2); // returns true
o2.equals(o1); //returns true

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Q1429. Explain Transitive equals contract.

Ans. The equals contract is said to be transitive if

obj1.equals(obj2); and obj2(.equals(obj3)

then obj1.equals(obj3) also returns true.

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Q1430. How will you enable or disable assertion for a package during runtime ?

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Q1431. Which java version supports assertion ?

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Q1432. Create an event class in Java.

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Q1433. How does multi threading improve performance ?

Ans. Every process in it's timeline require different resources. Utilization of resources can be optimized when they are shared among different processes or threads. When one thread is sleeping waiting for a peripheral to complete (e.g. a disk write, or a key press from the keyboard), other threads can continue using processor time and hence would lead to better usage of resources.

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Q1434. What are the different ways to avoid multi Threading related problems in Java ?

Ans. Synchronization,
Concurrent classes,
Volatile keyword,
Implementing concurrent Lock interface,
Immutable classes

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Q1435. What is context switching wrt Threads in Java?

Ans. Context Switching is the process of storing and restoring of CPU state so that Thread execution can be resumed from the same point at a later point of time.

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Q1436. What is Lock interface in Java Concurrency API ?

Ans. Lock interface provide more extensive locking. They allow more flexible structuring and may support multiple associated Condition objects.

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Q1437. Why Concurrent Collection Classes are fail-fast in Java ?

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Q1438. Can a class extend itself in Java ?

Ans. No

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Q1439. What is method hiding in Java ?

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Q1440. Can you prevent overriding a method without using final modifier or without declaring it private ?

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