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Quizzes – Java Collections

The following Java exercise(s) are designed to help you understand the article to which it belongs. If the following quizzes are too hard, then I recommend to read the article first, which offers a theoretical explanation including examples and exercises.

Articles: ArrayList  HashSet  TreeSet  HashMap  TreeMap 
Quizzes: Java Collection Quizzes 

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Quiz 1: Learn more about Java ArrayLists

What is written to the standard output as the result of executing the following code?

import java.util.ArrayList;

public class MyClass {

	public static void main(String[] args){
		ArrayList<String> prLanguage = new ArrayList<String>();
		prLanguage.add("Java");
		prLanguage.add("C++");
		prLanguage.add("Python");
		prLanguage.add("PHP");
		prLanguage.add("Ruby");
		prLanguage.add("Perl");

		prLanguage.add(3,null);
		prLanguage.add(3,null);
		prLanguage.add(4,"PHP");

		for(int i = 0; i &lt; prLanguage.size(); i ++ ) {
			System.out.print(" " + prLanguage.get(i));
		}
	}
}

Select the correct answer.


 

Quiz 2: How the elements of a TreeMap behave?

What is written to the standard output as the result of executing the following code?

import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;

public class MyClass {

	public static void main(String[] args){

		TreeMap countryMap = new TreeMap();
		countryMap.put("US","United States");
		countryMap.put("CN","China");
		countryMap.put("RU","Russia");
		countryMap.put("FR","France");
		countryMap.put("FR","France");
		countryMap.put("DE","Germany");
		countryMap.put("AU","Australia");
		countryMap.put("Au","Australia");
		countryMap.put("NU",null);

		Set set = countryMap.entrySet();
		Iterator iter = set.iterator();
		while(iter.hasNext()) {
			Map.Entry entry = (Map.Entry) iter.next();
			System.out.print(" " + entry.getValue());
		}
	}
}

Select the correct answer.


 

Quiz 3: An easy example using a HashSet

What is written to the standard output as the result of executing the following code?

import java.util.HashSet;
import java.util.Iterator;

public class MyClass {

	public static void main(String[] args){

		HashSet<String> citySet = new HashSet<String>();
		citySet.add(" Shanghai,");
		citySet.add(" Delhi,");
		citySet.add(" " + null + ",");
		citySet.add(" Moscow,");
		citySet.add(" London,");
		citySet.add(" New York,");
		citySet.add(" London,");

		Iterator<String> iter = citySet.iterator();
		while(iter.hasNext()) {
			System.out.print(" " + iter.next());
		}
	}
}

Select the correct answer.



Please, leave your questions, feedback and suggestions in the comments below! If you need more explanation by any of the answers, just let me know to update it for you!

Articles: ArrayList  HashSet  TreeSet  HashMap  TreeMap 
Quizzes: Java Collection Quizzes 
Megisoft.com offers a practical method to learn and improve your Java skills. It avoids unnecessary long boring theoretical explanations, but it uses many exercises and quizzes. The author of Megisoft is Sar Maroof who has more than a decade of experience with web development mainly with Java, MySql, HTML and more..

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Author: Sar Maroof
More than a decade of experience with developing web applications mainly with Java.
Sun Certified JSP as well as EJB
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Applied Science in Physics HBO Amsterdam
Bachellor Science in Physics at Basra university.
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  1. Your articles are for when it abeulotsly, positively, needs to be understood overnight.

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