Java Archives | Page 13 of 15 | 800+ Java & Big Data Interview Q&As

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Multithreading interview Q&As on differences between X and Y

Q1. What is difference between ‘Executor.submit()’ and ‘Executor.execute()’ method ? A1. The difference is that execute() doesn’t return a “Future” object, so you can’t wait for the completion of the Runnable, and get any exception it throws. The submit(…) method accepts Callable<V> and returns an instance of Future<V>, … Read...

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Non-trival Java 8 tutorial to appreciate the power of functional programming (FP)

Prerequisite: Understanding of Java 8 streams.

Q. You have a list of key value pairs (“student name”, “subject”) as shown below.

Input

("Sam Peter", "English"),
("Sam Peter", "Science"),
("John English", "Science"),
("Neil Graham", "Maths"),
("Neil Graham", "Arts"),
("Neil Graham", "Music")

("Sam Peter", "English"),

("Sam Peter", "Science"),

("John English", "Science"),

("Neil Graham", "Maths"),

("Neil Graham", "Arts"),

("Neil Graham", "Music")

The required task is to list all the subjects for each student as shown below.

Result

"Samp Pter"    --> [English, Science]
"John English" --> [Science]
"Neil Graham"  --> [Maths, Arts, Music]

"Samp Pter" --> [English, Science]

"John English" --> [Science]

"Neil Graham" --> [Maths, Arts, Music]

…

Object equals Vs == and pass by reference Vs value

Q1. What is the difference between “==” and equals(..) method when comparing 2 objects?
A1.It is important to understand the difference between identity (i.e. ==) comparison, which is a shallow comparison that compares only the object references, and the equals( ) comparison,

…

Processing large files efficiently – BigData & Hadoop – part 3

Q1. What are the different data sizes, and what technologies can be used to process them? A1. In general, data sizes can be classified as shown below. 1) Small size data is < 10 GB in multiple files. … Read more ›...

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Processing large files efficiently in Java – multi-threaded code – part 2

If you want to process medium sized data (e.g. 2 GB to 100 GB in multiple files) in Java, consider writing a batch job with Spring batch or Java EE 7.0 batch processing. If processing requires access to other systems, use “spring integration” … Read more ›...

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Producer and Consumer Java Multi-threading code

The following code is used for demonstrating thread-safety issues on eclipse.

Step 1: ProducerConsumerTest

package com.debug.multithread;

public class ProducerConsumerTest {
    
    
    public static void main(String[] args) throws InterruptedException {
        
        ProducerConsumer pc = new ProducerConsumer();
        
        //spawn a new producer thread and start
        Thread producer = new Thread(new ProducerThread(pc));
        producer.start();
        
        Thread.sleep(10); //main thread sleeps for 1 second
        
        //spawn a new consumer thread and start
        Thread consumer = new Thread(new ConsumerThread(pc));
        consumer.start();
        
    }
}

package com.debug.multithread;

public class ProducerConsumerTest {

public static void main(String[] args) throws InterruptedException {

ProducerConsumer pc = new ProducerConsumer();

//spawn a new producer thread and start

Thread producer = new Thread(new ProducerThread(pc));

producer.start();

Thread.sleep(10); //main thread sleeps for 1 second

//spawn a new consumer thread and start

Thread consumer = new Thread(new ConsumerThread(pc));

consumer.start();

}

Step 2: Producer thread.

package com.debug.multithread;

public class ProducerThread implements Runnable {

    private ProducerConsumer pc;

    public ProducerThread(ProducerConsumer pc) {
        this.pc = pc;
    }

    @Override
    public void run() {
        pc.produce();
    }

}

package com.debug.multithread;

public class ProducerThread implements Runnable {

private ProducerConsumer pc;

public ProducerThread(ProducerConsumer pc) {

this.pc = pc;

}

@Override

public void run() {

pc.produce();

}

Step 3: Consumer thread.

package com.debug.multithread;

public class ConsumerThread implements Runnable {

    private ProducerConsumer pc;
        
    public ConsumerThread(ProducerConsumer pc) {
        this.pc = pc;
    }

    @Override
    public void run() {
        pc.consume();
    }

}

package com.debug.multithread;

public class ConsumerThread implements Runnable {

private ProducerConsumer pc;

public ConsumerThread(ProducerConsumer pc) {

this.pc = pc;

}

@Override

public void run() {

pc.consume();

}

Step 4: ProducerConsumer logic.

…

Q1 – Q10 Java OOPs interview Q&As

If you don’t get Java OOPs interview questions & answers right in the job interviews you can say OOPS !!!! to your Java interview success. Q1. Is Java a 100% Object Oriented (OO) language? if yes why? and if no, why not? A1. … Read more ›...

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Q6 – Q11 Swing interview questions and answers

Extends Q1 to Q5 Swing interview questions and answers.

Q6. If you add a component to the CENTER of a border layout, which directions will the component stretch?
A6. The component will stretch both horizontally and vertically. It will occupy the whole space in the middle.

…

QoS & SLAs interview Q&As on Availability, Serviceability, Fault tolerance & Disaster Recoverability – Non Functional Requirements

Q1. What are the system qualities that typically form a basis for QoS requirements? A1. Quality of service (QoS) covers Non Functional requirements such as As microservices use disparate datasources like SQL store, NoSQL store, Cache, Object store like AWS S3, … Read more ›...

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Read a text file from Java classpath

File to read: src/main/resources/examples/request.xml

<employee>
    <name>Peter Smith</name>
    <age>25</age>
</employee>

<name>Peter Smith</name>

</employee>

1. Using Java API without any libraries

package com.mytutorial;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;


public class ReadTextFileFromClasspath {

    public static void main(String[] args) throws IOException {
        InputStream is = ReadTextFileFromClasspath.class.getResourceAsStream("/examples/request.xml");
        InputStreamReader isr = new InputStreamReader(is);
        StringBuilder sb=new StringBuilder();
        BufferedReader br = new BufferedReader(isr);
        String read = br.readLine();

        while(read != null) {
            sb.append(read);
            read =br.readLine();
            sb.append("\n");
        }

        System.out.println(sb.toString());
    }
}

package com.mytutorial;

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

public class ReadTextFileFromClasspath {

public static void main(String[] args) throws IOException {

InputStream is = ReadTextFileFromClasspath.class.getResourceAsStream("/examples/request.xml");

InputStreamReader isr = new InputStreamReader(is);

StringBuilder sb=new StringBuilder();

BufferedReader br = new BufferedReader(isr);

String read = br.readLine();

while(read != null) {

sb.append(read);

read =br.readLine();

sb.append("\n");

}

System.out.println(sb.toString());

}

You can also use the “ClassLoader”

ClassLoader loader = Thread.currentThread().getContextClassLoader();
InputStream is = loader.getResourceAsStream("examples/request.xml");

1 2	ClassLoader loader = Thread.currentThread().getContextClassLoader(); InputStream is = loader.getResourceAsStream("examples/request.xml");

2. Using Java 7 NIO

 package com.mytutorial;

import java.io.IOException;
import java.net.URISyntaxException;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;


public class ReadTextFileFromClasspath {

    public static void main(String[] args) throws IOException, URISyntaxException {

        List<String> readLines = Files.readAllLines(
            Paths.get(ReadTextFileFromClasspath.class.getResource("/examples/request.xml").toURI()), Charset.defaultCharset());

        System.out.println(readLines);
    }
}

package com.mytutorial;

import java.io.IOException;

import java.net.URISyntaxException;

import java.nio.charset.Charset;

import java.nio.file.Files;

import java.nio.file.Paths;

import java.util.List;

public class ReadTextFileFromClasspath {

public static void main(String[] args) throws IOException, URISyntaxException {

List<String> readLines = Files.readAllLines(

Paths.get(ReadTextFileFromClasspath.class.getResource("/examples/request.xml").toURI()), Charset.defaultCharset());

System.out.println(readLines);

}

…

Reading a text file in Java with the Scanner

As a Java developer it is a very common task to read file contents to a String object. It is also very common in pre-interview written tests read the contents of a file and apply regex to split string, etc.

4 things to watch-out for in File processing

1) Files must be closed once read.

…

Reloading configuration files in Java without stopping the server

Q1. Why & when do you want to use properties files for the project configuration as opposed to Java constants?
A1. It is a best practice to externalize application related properties that are likely to change. If you hard code the properties that are likely to change,

…

Searching algorithms in Java

This assumes that you understand “Swapping, partitioning, and sorting algorithms in Java“. Q1. Can you write a code to search for number 5 in 7 3 6 8 2 9 5 4? A1. The code below uses the linear search algorithm. … Read more ›...

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« 1 … 9 10 11 12 13 14 15 »

Blog Archives

Multithreading interview Q&As on differences between X and Y

Non-trival Java 8 tutorial to appreciate the power of functional programming (FP)

Object equals Vs == and pass by reference Vs value

Processing large files efficiently – BigData & Hadoop – part 3

Processing large files efficiently in Java – multi-threaded code – part 2

Producer and Consumer Java Multi-threading code

Q1 – Q10 Java OOPs interview Q&As

Q6 – Q11 Swing interview questions and answers

QoS & SLAs interview Q&As on Availability, Serviceability, Fault tolerance & Disaster Recoverability – Non Functional Requirements

Read a text file from Java classpath

Reading a text file in Java with the Scanner

Reloading configuration files in Java without stopping the server

Searching algorithms in Java

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