Java8 Programming Examples

Java Program to create an array with randomly shuffled numbers

java8

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
public class Demo {
	public static void main(String args[]) {
		List<Integer>list = new ArrayList<Integer>();
		list.add(10);
		list.add(50);
		list.add(100);
		list.add(150);
		list.add(200);
		list.add(350);
		list.add(500);
		list.add(800);
		list.add(1000);
		Collections.shuffle(list);
		int len = list.size();
		int[] res = new int[len];
		for (int i = 0; i<len; i++) {
			res[i] = list.get(i);
		}
		System.out.println("Randomly shuffled array elements = "+Arrays.toString(res));
	}
}

Java Program to get maximum value with Comparator

java8

import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
public class Demo {
	@SuppressWarnings("unchecked")
	public static void main(String args[]) {
		Integer arr[] = { 40, 20, 30, 10, 90, 60, 70 };
		List list = Arrays.asList(arr);
		Comparator comp = Collections.reverseOrder();
		System.out.println("Maximum element = "+Collections.min(list, comp));
	}
}

Java Program to extend the size of an Integer array

java8

public class Demo {
	public static void main(String[] args) {
		Integer[] arr = new Integer[] { 50, 100, 150, 200, 400, 500, 800, 1000};
		System.out.println("All the elements before extending the array...");
		for (Integer i:arr)
			System.out.println(i);
			Integer[] new_size = new Integer[15];
			new_size[8] = 2000;
			new_size[9] = 3000;
			new_size[10] = 4000;
			new_size[11] = 5000;
			new_size[12] = 6000;
			new_size[13] = 9000;
			new_size[14] = 10000;
			System.arraycopy(arr, 0, new_size, 0, arr.length);
			System.out.println("All the elements after extending the array...");
			for (Integer i: new_size)
				System.out.println(i);
	}
}

Copy one array from another in Java

java8

public class Demo {
	public static void main(String[] args) {
		String[] arr = new String[] { "P","Q", "R", "S", "T"};
		System.out.println("Initial array...");
		for (int i = 0; i<arr.length; i++)
			System.out.println(arr[i]);
			int len = arr.length;
			String[] arr2 = new String[len];
			System.arraycopy(arr, 0, arr2, 0, arr.length);
			System.out.println("New array...copied");
			for (int i = 0; i<arr2.length; i++)
				System.out.println(arr2[i]);
	}
}

Java Program to convert an Array to a List

java8

import java.util.Arrays;
import java.util.List;
public class Demo {
	public static void main(String[] args) {
		Integer[] arr = {10, 20, 30, 40, 50, 60, 70, 80, 90, 100};
		System.out.println("Array...");
		for (Integer res: arr) {
			System.out.println(res);
		}
		System.out.println("List...");
		List<Integer>list = Arrays.asList(arr);
		for (Integer res: list) {
			System.out.println(res);
		}
	}
}

Java Program to sort integers in unsorted array

java8

import java.util.Arrays;
public class Demo {
	public static void main(String[] args) {
		int[] arr = { 10, 14, 28, 11, 7, 16, 30, 50, 25, 18};
		System.out.println("The unsorted integer array = "+Arrays.toString(arr));
		int[] res = arr;
		Arrays.sort(res);
		System.out.println("The sorted integer array = "+Arrays.toString(res));
	}
}

Java Program to sort a subset of array elements

java8

import java.util.Arrays;
public class Demo {
	public static void main(String[] args) {
		String[] strArr = new String[] { "r", "p", "v","y", "s", "q" };
		Arrays.sort(strArr, 2, 6);
		System.out.println("Sorted subset of array elements from index 2 to 6...");
		for (int a = 0; a<strArr.length; a++) {
			System.out.println(strArr[a]);
		}
	}
}

Program to calculate the time of sorting an array

java8

import java.util.Arrays;
import java.util.Date;
public class Demo {
	public static void main(String[] args) {
		int[] arr = new int[1000];
		for (int i = 0; i<arr.length; i++) {
			arr[i] = (int) (i + 20);
		}
		Date past = new Date();
		Arrays.sort(arr);
		Date future = new Date();
		System.out.println("Time (milliseconds) = " + (future.getTime() - past.getTime()));
	}
}

Populate a 2d array with random alphabetic values in Java

java8

import java.util.Arrays;
import java.util.Random;
public class Demo {
	public static void main(String[] args) {
		char arr[][] = new char[3][3];
		Random randNum = new Random();
		for (int i = 0; i< 3; i++) {
			for (int j = 0; j< 3; j++) {
				int x = randNum.nextInt(3);
				switch (x) {
					case 0: {
						arr[i][j] = 'p';
						break;
					}
					case 1: {
						arr[i][j] = 'q';
						break;
					}
					case 2: {
						arr[i][j] = 'r';
						break;
					}
					case 3: {
						arr[i][j] = 's';
						break;
					}
					case 4: {
						arr[i][j] = 't';
						break;
					}
					case 5: {
						arr[i][j] = 'u';
						break;
					}
					case 6: {
						arr[i][j] = 'v';
						break;
					}
					case 7: {
						arr[i][j] = 'w';
						break;
					}
				}
			}
		}
		System.out.println("Random alphabets...");
		System.out.println(Arrays.deepToString(arr));
	}
}

Java Program to output fixed number of array elements in a line

java8

public class Demo {
	public static void main(String[] args) {
		int[] list = new int[50];
		for (int i = 0; i<list.length; i++) {
			list[i] = (int) (i + 20);
		}
		int output = 0;
		for (int i = 0; i<list.length; i++) {
			if (output == 5) {
				System.out.println();
				output = 0;
			}
			System.out.print(list[i] + ", ");
			output++;
		}
	}
}

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