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Commit caebf86

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add Stream related solutions
1 parent 63b6553 commit caebf86

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8 files changed

+152
-1
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8 files changed

+152
-1
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package CreatingStreams;
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import java.util.Arrays;
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import java.util.List;
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import java.util.stream.Collectors;
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import java.util.stream.Stream;
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public class CreatingStreams {
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public static void main(String[] args) {
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// A stream consists of a source followed by zero or more intermediate methods combined together(pipelined) and
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// a terminal method to process the objects obtained from the source as per the methods described.
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// Stream is used to compute elements as per the pipelined methods without altering the original value of the object.
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Stream<Integer> stream = Stream.of(1,2,3,4,5); // Stream using Stream.of()
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stream.forEach(System.out::println);
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int []arr = {2,4,8,16};
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int sum = Arrays.stream(arr).sum(); // Stream from array
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System.out.println(sum);
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List<Integer> numbers = Arrays.asList(1,3,5,7);
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numbers.stream().map(i -> i+1).collect(Collectors.toList()).forEach(System.out::println); // Stream from collection
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}
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}
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package ExceptionHandlingBestPractices;
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public class ListOfBestPractices {
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// Use specific exception classes for different types of errors
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// Catch exceptions at the appropriate level of abstraction
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// Log and handle exceptions in a consistent and informative manner
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// Avoid empty catch blocks and swallowing exceptions
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// Propagate exceptions up the call stack when appropriate
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// Use finally blocks for cleanup and resource management
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// Use a global exception handler
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// Don’t close resources manually
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}

‎More Core Java Concepts to Know/FunctionalInterfacesInJDK/FuncInterfacesDemo.java

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System.out.println(supplier.get());
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}
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}
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}
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package InfiniteStreams;
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import java.util.Random;
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import java.util.stream.IntStream;
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public class InfiniteStreams {
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public static void main(String[] args) {
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IntStream
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.iterate(0, i -> i+1)
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.forEach(System.out::println);
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Random random = new Random();
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IntStream.generate(random::nextInt).forEach(System.out::println);
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}
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}
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package StreamAPIForFilteringAndTransformation;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.stream.Collectors;
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public class FilteringAndTransformation {
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public static void main(String[] args) {
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List<Integer> numbers = new ArrayList<>();
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numbers.add(1);
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numbers.add(2);
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numbers.add(3);
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numbers.add(4);
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numbers.add(5);
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List evenNumbers = numbers.stream().filter(e -> e % 2 == 0).map(e -> e*e).collect(Collectors.toList());
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System.out.println(evenNumbers);
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}
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}
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package StreamAPIForGroupingAndAggregation;
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public class Employee {
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private String name;
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private String department;
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private double salary;
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public Employee(String name, String department, double salary) {
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this.name = name;
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this.department = department;
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this.salary = salary;
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}
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public String getDepartment() {
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return department;
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}
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public double getSalary() {
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return salary;
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}
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@Override
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public String toString() {
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return name;
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}
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}
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package StreamAPIForGroupingAndAggregation;
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import java.util.ArrayList;
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import java.util.DoubleSummaryStatistics;
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import java.util.List;
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import java.util.stream.Collectors;
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public class GroupingAndAggregation {
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public static void main(String[] args) {
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List<Employee> employees = new ArrayList<>();
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employees.add(new Employee("Imam", "Technical", 10000));
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employees.add(new Employee("Biplob", "HR", 9000));
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employees.add(new Employee("Rakib", "Technical", 8000));
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var groupedEmployees = employees.stream()
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.collect(Collectors.groupingBy(Employee::getDepartment,
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Collectors.averagingDouble(Employee::getSalary)));
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System.out.println(groupedEmployees); // Average salary for all departments
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DoubleSummaryStatistics summary = employees.stream().mapToDouble(Employee::getSalary).summaryStatistics();
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System.out.println(summary.getAverage()); // Average salary for all employees
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}
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}
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package StreamIntermediateAndTerminalOps;
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import StreamAPIForGroupingAndAggregation.Employee;
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import java.util.Arrays;
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import java.util.Comparator;
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import java.util.List;
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import java.util.stream.Collectors;
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public class StreamOps {
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public static void main(String[] args) {
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List<Integer> numbers = Arrays.asList(64,1,2,4,8,16,32);
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int sumOfFilteredNumbers = numbers.stream()
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.filter(n -> n%4==0)
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.map(n -> n*n)
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.reduce(0,(sum,i) -> sum+i);
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System.out.println(sumOfFilteredNumbers);
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numbers.stream()
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.sorted()
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.collect(Collectors.toList())
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.forEach(System.out::println);
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List<Employee> employees = List.of(new Employee("Imam", "Technical", 10000),
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new Employee("Biplob", "HR", 9000),
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new Employee("Rakib", "Technical", 8000));
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employees.stream()
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.sorted(Comparator.comparing(Employee::getSalary))
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.forEach(System.out::println);
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}
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}

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