JetBrains Academy: Set - Kamil-Jankowski/Learning-JAVA GitHub Wiki
Creating a set:
Create TreeSet by name set in any way known to you and fill it with the following three strings "Gamma", "Alpha", "Omega" .
The code for displaying the set is already written.
import java.util.*;
public class Main {
public static void main(String[] args) {
TreeSet<String> set = new TreeSet<>();
set.add("Gamma");
set.add("Alpha");
set.add("Omega");
System.out.println(set);
}
}Output elements:
The set of strings is given.
Set<String> nameSet = new TreeSet<>(Arrays.asList("Mr.Green", "Mr.Yellow", "Mr.Red"));
Output each its element in the loop with a new line.
import java.util.*;
public class Main {
public static void main(String[] args) {
Set<String> nameSet = new TreeSet<>(Arrays.asList("Mr.Green", "Mr.Yellow", "Mr.Red"));
for(String name : nameSet){
System.out.println(name);
}
}
}Symmetric difference:
Implement a method for finding the symmetric difference of two given sets. Elements in the resulting set can be in any order.
import java.util.*;
class SetUtils {
/**
* @return symmetric difference between set1 and set2
*/
public static <T> Set<T> symmetricDifference(Set<? extends T> set1, Set<? extends T> set2) {
Set<T> difference = new HashSet<>();
for (T element : set1) {
if(!(set2.contains(element))){
difference.add(element);
}
}
for (T element : set2) {
if(!(set1.contains(element))){
difference.add(element);
}
}
return difference;
}
}
/* Do not change code below */
public class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
String strSet1 = scanner.nextLine();
String strSet2 = scanner.nextLine();
Set<String> set1 = new HashSet<>();
Set<String> set2 = new HashSet<>();
if (!strSet1.equals("empty")){
Collections.addAll(set1, strSet1.split(" "));
}
if (!strSet2.equals("empty")){
Collections.addAll(set2, strSet2.split(" "));
}
Set<String> resultSet = SetUtils.symmetricDifference(set1, set2);
resultSet.forEach(e -> System.out.print(e + " "));
}
}Processing sets:
Implement two methods. The first method should create a set from a string of numbers separated by a space. The second method should remove all numbers greater than 10 from the given set.
import java.util.*;
class SetUtils {
public static Set<Integer> getSetFromString(String str) {
String[] input = str.split(" ");
SortedSet<Integer> numbers = new TreeSet<>();
for (String s : input) {
numbers.add(Integer.parseInt(String.valueOf(s)));
}
return numbers;
}
public static void removeAllNumbersGreaterThan10(Set<Integer> set) {
set.removeIf((Integer element) -> element > 10);
}
}
/* Do not change code below */
public class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
String numbers = scanner.nextLine();
Set<Integer> set = SetUtils.getSetFromString(numbers);
SetUtils.removeAllNumbersGreaterThan10(set);
set.forEach(e -> System.out.print(e + " "));
}
}Removing duplicates and sorting:
Write a program that reads a sequence of strings from the standard input and displays them in a lexicographic order without duplicates.
Try to write your solution using a set.
Input data format:
The first line contains the size of a string sequence. Next lines contain strings.
Output data format:
A sorted sequence of strings without duplicates. Each string must be in a new line.
import java.util.*;
class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int lines = scanner.nextInt();
scanner.nextLine();
SortedSet<String> sortedSet = new TreeSet<>();
for (int i = 0; i < lines ; i++){
sortedSet.add(scanner.nextLine());
}
for (String s : sortedSet){
System.out.println(s);
}
}
}