//1
import java.util.*;
import java.util.stream.*;
public class FirstNonRepeatedChar {
public static void main(String[] args) {
String input = "swiss";
// Find the first non-repeated character using streams
Optional<Character> firstNonRepeated = input.chars() // Convert string to an IntStream
.mapToObj(c -> (char) c) // Convert int to Character
.collect(Collectors.groupingBy(c -> c, LinkedHashMap::new, Collectors.counting())) // Group by character and count occurrences
.entrySet() // Get entries of the map
.stream() // Convert to a stream
.filter(entry -> entry.getValue() == 1) // Filter to get only non-repeated characters
.map(Map.Entry::getKey) // Get the character from the entry
.findFirst(); // Find the first non-repeated character
// Print the result
firstNonRepeated.ifPresent(System.out::println); // Will print the first non-repeated character
}
}
o/p:w
//2
import java.util.*;
import java.util.stream.*;
public class PrintDuplicates {
public static void main(String[] args) {
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 2, 3, 7, 8, 9, 1, 5);
// Find and print the duplicate numbers using Java 8 streams
numbers.stream()
.collect(Collectors.groupingBy(n -> n, Collectors.counting())) // Group numbers and count occurrences
.entrySet()
.stream()
.filter(entry -> entry.getValue() > 1) // Keep only numbers with count > 1
.map(Map.Entry::getKey) // Extract the number
.forEach(System.out::println); // Print each duplicate number
}
}
from input:[1, 2, 3, 4, 5, 6, 2, 3, 7, 8, 9, 1, 5]
o/p:
1
2
3
5
//3
import java.util.*;
import java.util.stream.*;
public class PalindromeChecker {
public static void main(String[] args) {
// Example string and number
String str = "madam";
int number = 121;
// Check if string is a palindrome
if (isPalindrome(str)) {
System.out.println(str + " is a palindrome.");
} else {
System.out.println(str + " is not a palindrome.");
}
// Check if number is a palindrome
if (isPalindrome(number)) {
System.out.println(number + " is a palindrome.");
} else {
System.out.println(number + " is not a palindrome.");
}
}
// Method to check if a string is a palindrome using Java 8
public static boolean isPalindrome(String str) {
// Create a stream from the string, reverse it, and check equality
String reversed = str.chars() // Create an IntStream from the string
.mapToObj(c -> (char) c) // Convert each int to a Character
.collect(StringBuilder::new, StringBuilder::append, StringBuilder::append) // Collect into StringBuilder
.reverse() // Reverse the StringBuilder
.toString(); // Convert it back to a string
return str.equals(reversed); // Check if the original string is equal to the reversed string
}
// Method to check if a number is a palindrome using Java 8
public static boolean isPalindrome(int number) {
// Convert the number to a string
String str = Integer.toString(number);
return isPalindrome(str); // Reuse the string palindrome check method
}
}
madam is a palindrome.
121 is a palindrome.
hello is not a palindrome.
123 is not a palindrome.
//4
import java.util.*;
import java.util.stream.*;
public class FirstRepeatedCharacter {
public static void main(String[] args) {
String input = "java articles are awesome";
// Find the first repeated character using streams
Optional<Character> firstRepeatedChar = input.chars() // Convert the string to IntStream
.mapToObj(c -> (char) c) // Convert int to Character
.filter(c -> c != ' ') // Exclude spaces if needed (optional)
.collect(Collectors.toMap(c -> c, c -> 1, Integer::sum)) // Map each char, count occurrences
.entrySet() // Get the entries
.stream() // Convert to stream
.filter(entry -> entry.getValue() > 1) // Keep only characters with count > 1
.map(Map.Entry::getKey) // Extract the character
.findFirst(); // Get the first repeated character
// Output the result
firstRepeatedChar.ifPresent(c -> System.out.println("First repeated character: " + c));
}
}
input:"java articles are awesome"
o/p:First repeated character: a
//5
import java.util.*;
import java.util.stream.*;
public class MinMaxArray {
public static void main(String[] args) {
// Example array
int[] numbers = {12, 45, 23, 56, 89, 1, 34, 78};
// Find the minimum and maximum values using Java 8 streams
OptionalInt min = Arrays.stream(numbers) // Create an IntStream from the array
.min(); // Find the minimum value
OptionalInt max = Arrays.stream(numbers) // Create an IntStream from the array
.max(); // Find the maximum value
// Print the results
min.ifPresent(m -> System.out.println("Minimum value: " + m));
max.ifPresent(m -> System.out.println("Maximum value: " + m));
}
}
//for the array:{12, 45, 23, 56, 89, 1, 34, 78}
o:p:Minimum value: 1
Maximum value: 89
//6
import java.util.*;
import java.util.stream.*;
public class SecondHighestNumber {
public static void main(String[] args) {
// Example array
int[] numbers = {12, 45, 23, 56, 89, 1, 34, 78, 56};
// Find the second highest number using Java 8 streams
OptionalInt secondHighest = Arrays.stream(numbers) // Create an IntStream from the array
.distinct() // Remove duplicates
.sorted() // Sort the stream
.skip(Math.max(0, numbers.length - 2)) // Skip all but the last two elements
.findFirst(); // Get the second-to-last element
// Print the result
secondHighest.ifPresentOrElse(
num -> System.out.println("Second highest number: " + num),
() -> System.out.println("There is no second highest number.")
);
}
}
from an array:{12, 45, 23, 56, 89, 1, 34, 78, 56}
o/p:Second highest number: 78
//7
import java.util.*;
import java.util.stream.*;
public class SecondLowestNumber {
public static void main(String[] args) {
// Example array
int[] numbers = {12, 45, 23, 56, 89, 1, 34, 78, 1};
// Find the second lowest number using Java 8 streams
OptionalInt secondLowest = Arrays.stream(numbers) // Create an IntStream from the array
.distinct() // Remove duplicates
.sorted() // Sort the stream in ascending order
.skip(1) // Skip the first (lowest) element
.findFirst(); // Get the first element (second lowest)
// Print the result
secondLowest.ifPresentOrElse(
num -> System.out.println("Second lowest number: " + num),
() -> System.out.println("There is no second lowest number.")
);
}
}
from an array:{12, 45, 23, 56, 89, 1, 34, 78, 1}
Second lowest number: 12
//8
import java.time.*;
public class CurrentDateTime {
public static void main(String[] args) {
// Get the current date and time
LocalDateTime currentDateTime = LocalDateTime.now();
// Print the current date and time
System.out.println("Current date and time: " + currentDateTime);
// Optionally, you can also format the date and time
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
String formattedDateTime = currentDateTime.format(formatter);
System.out.println("Formatted date and time: " + formattedDateTime);
}
}
Current date and time: 2024-11-19T14:30:00.123
Formatted date and time: 2024-11-19 14:30:00
//9
import java.util.stream.*;
public class First10EvenNumbers {
public static void main(String[] args) {
// Generate the first 10 even numbers using Java 8 streams
Stream.iterate(2, n -> n + 2) // Start from 2, and keep adding 2 to get the next even number
.limit(10) // Limit the stream to the first 10 elements
.forEach(System.out::println); // Print each even number
}
}
2
4
6
8
10
12
14
16
18
20
//10
import java.util.*;
import java.util.stream.*;
public class ContainsDuplicate {
public static void main(String[] args) {
// Example list of integers
List<Integer> nums = Arrays.asList(1, 2, 3, 4, 5, 1);
// Check if there are any duplicates using Java 8 streams
boolean hasDuplicates = nums.stream() // Create a stream from the list
.collect(Collectors.groupingBy(n -> n, Collectors.counting())) // Group by each number and count occurrences
.values() // Get the counts of each element
.stream() // Convert to a stream of counts
.anyMatch(count -> count > 1); // Check if any count is greater than 1
// Output the result
System.out.println("Contains duplicates: " + hasDuplicates);
}
}
Example Output:
For the list:
{1, 2, 3, 4, 5, 1}
The output will be:
Contains duplicates: true
For a list with distinct elements:
{1, 2, 3, 4, 5}
The output will be:
Contains duplicates: false
//11
import java.util.*;
import java.util.stream.*;
public class SortListDescending {
public static void main(String[] args) {
// Example list of integers
List<Integer> nums = Arrays.asList(12, 45, 23, 56, 89, 1, 34, 78);
// Sort the list in descending order using Java 8 streams
List<Integer> sortedList = nums.stream() // Create a stream from the list
.sorted(Comparator.reverseOrder()) // Sort the stream in descending order
.collect(Collectors.toList()); // Collect the sorted elements into a new list
// Output the sorted list
System.out.println("Sorted list in descending order: " + sortedList);
}
}
{12, 45, 23, 56, 89, 1, 34, 78}
Sorted list in descending order: [89, 78, 56, 45, 34, 23, 12, 1]
//12
import java.util.*;
import java.util.stream.*;
public class ConcatenateStreams {
public static void main(String[] args) {
// Example lists to convert to streams
List<Integer> list1 = Arrays.asList(1, 2, 3, 4);
List<Integer> list2 = Arrays.asList(5, 6, 7, 8);
// Convert lists to streams and concatenate them
Stream<Integer> concatenatedStream = Stream.concat(list1.stream(), list2.stream());
// Print the concatenated stream
concatenatedStream.forEach(System.out::println);
}
}
list1 = {1, 2, 3, 4}
list2 = {5, 6, 7, 8}
1
2
3
4
5
6
7
8
//13
import java.util.*;
import java.util.stream.*;
public class SumListWithInitialValue {
public static void main(String[] args) {
// Example list of integers
List<Integer> nums = Arrays.asList(1, 2, 3, 4, 5);
// Sum the elements of the list with an initial value of 100
int sumWithInitialValue = nums.stream()
.reduce(100, Integer::sum); // 100 is the initial value, Integer::sum is the accumulator
// Output the result
System.out.println("Sum with initial value 100: " + sumWithInitialValue);
}
}
{1, 2, 3, 4, 5}
Sum with initial value 100: 115
//14
import java.util.*;
import java.util.stream.*;
public class CountElements {
public static void main(String[] args) {
// Example list of integers
List<Integer> nums = Arrays.asList(1, 2, 3, 4, 5, 6);
// Use stream to count the number of elements
long count = nums.stream()
.count(); // count the elements in the stream
// Output the result
System.out.println("Total number of elements: " + count);
}
}
{1, 2, 3, 4, 5, 6}
Total number of elements: 6
Write, Run & Share Java code online using OneCompiler's Java online compiler for free. It's one of the robust, feature-rich online compilers for Java language, running the Java LTS version 17. Getting started with the OneCompiler's Java editor is easy and fast. The editor shows sample boilerplate code when you choose language as Java and start coding.
OneCompiler's Java online editor supports stdin and users can give inputs to the programs using the STDIN textbox under the I/O tab. Using Scanner class in Java program, you can read the inputs. Following is a sample program that shows reading STDIN ( A string in this case ).
import java.util.Scanner;
class Input {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("Enter your name: ");
String inp = input.next();
System.out.println("Hello, " + inp);
}
}
OneCompiler supports Gradle for dependency management. Users can add dependencies in the build.gradle file and use them in their programs. When you add the dependencies for the first time, the first run might be a little slow as we download the dependencies, but the subsequent runs will be faster. Following sample Gradle configuration shows how to add dependencies
apply plugin:'application'
mainClassName = 'HelloWorld'
run { standardInput = System.in }
sourceSets { main { java { srcDir './' } } }
repositories {
jcenter()
}
dependencies {
// add dependencies here as below
implementation group: 'org.apache.commons', name: 'commons-lang3', version: '3.9'
}
Java is a very popular general-purpose programming language, it is class-based and object-oriented. Java was developed by James Gosling at Sun Microsystems ( later acquired by Oracle) the initial release of Java was in 1995. Java 17 is the latest long-term supported version (LTS). As of today, Java is the world's number one server programming language with a 12 million developer community, 5 million students studying worldwide and it's #1 choice for the cloud development.
short x = 999; // -32768 to 32767
int x = 99999; // -2147483648 to 2147483647
long x = 99999999999L; // -9223372036854775808 to 9223372036854775807
float x = 1.2;
double x = 99.99d;
byte x = 99; // -128 to 127
char x = 'A';
boolean x = true;
When ever you want to perform a set of operations based on a condition If-Else is used.
if(conditional-expression) {
// code
} else {
// code
}
Example:
int i = 10;
if(i % 2 == 0) {
System.out.println("i is even number");
} else {
System.out.println("i is odd number");
}
Switch is an alternative to If-Else-If ladder and to select one among many blocks of code.
switch(<conditional-expression>) {
case value1:
// code
break; // optional
case value2:
// code
break; // optional
...
default:
//code to be executed when all the above cases are not matched;
}
For loop is used to iterate a set of statements based on a condition. Usually for loop is preferred when number of iterations is known in advance.
for(Initialization; Condition; Increment/decrement){
//code
}
While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.
while(<condition>){
// code
}
Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.
do {
// code
} while (<condition>);
Class is the blueprint of an object, which is also referred as user-defined data type with variables and functions. Object is a basic unit in OOP, and is an instance of the class.
class keyword is required to create a class.
class Mobile {
public: // access specifier which specifies that accessibility of class members
string name; // string variable (attribute)
int price; // int variable (attribute)
};
Mobile m1 = new Mobile();
public class Greeting {
static void hello() {
System.out.println("Hello.. Happy learning!");
}
public static void main(String[] args) {
hello();
}
}
Collection is a group of objects which can be represented as a single unit. Collections are introduced to bring a unified common interface to all the objects.
Collection Framework was introduced since JDK 1.2 which is used to represent and manage Collections and it contains:
This framework also defines map interfaces and several classes in addition to Collections.
| Collection | Description |
|---|---|
| Set | Set is a collection of elements which can not contain duplicate values. Set is implemented in HashSets, LinkedHashSets, TreeSet etc |
| List | List is a ordered collection of elements which can have duplicates. Lists are classified into ArrayList, LinkedList, Vectors |
| Queue | FIFO approach, while instantiating Queue interface you can either choose LinkedList or PriorityQueue. |
| Deque | Deque(Double Ended Queue) is used to add or remove elements from both the ends of the Queue(both head and tail) |
| Map | Map contains key-values pairs which don't have any duplicates. Map is implemented in HashMap, TreeMap etc. |