Java8 Programming Examples

Java Program to fill an array with random numbers

java8

import java.util.Arrays;
import java.util.Random;
public class Demo {
	public static void main(String args[]) {
		double[] arr = new double[5];
		Random randNum = new Random();
		for (int i = 0; i< 5; i++) {
			arr[i] = randNum.nextInt();
		}
		System.out.println("Random numbers = "+Arrays.toString(arr));
	}
}

Java Program to shift array elements to the left

java8

import java.util.Arrays;
public class Demo {
	public static void main(String[] argv) throws Exception {
		int[] arr = { 10, 20, 30, 40, 50, 60, 70, 80, 90 };
		System.out.println("Initial array...\n"+Arrays.toString(arr));
		System.arraycopy(arr, 1, arr, 0, arr.length - 1);
		System.out.println("Array after shifting to the left...");
		System.out.println(Arrays.toString(arr));
	}
}

Java Program to create random BigInteger within a given range

java8

import java.math.BigInteger;
import java.util.Random;
public class Demo {
	public static void main(String[] args) {
		Random random = new Random();
		BigInteger i = new BigInteger(1024, random);
		System.out.println("Random BigInteger = "+i);
	}
}

Java Program to create a BigDecimal from a string type value

java8

import java.math.BigDecimal;
public class Demo {
	public static void main(String[] argv) throws Exception {
		BigDecimal one = new BigDecimal("562537627.8787867");
		BigDecimal two = BigDecimal.valueOf(562L);
		one = one.add(two);
		System.out.println(one);
	}
}

Java Program to adjust Adjust LocalDate to first Day Of next month

java8

import java.time.LocalDate;
import java.time.Month;
import java.time.temporal.TemporalAdjusters;
public class Demo {
	public static void main(String[] args) {
		LocalDate localDate = LocalDate.of(2019, Month.JUNE, 15);
		System.out.println("Current Date = "+localDate);
		System.out.println("Current Month = "+localDate.getMonth());
		LocalDate day = localDate.with(TemporalAdjusters.firstDayOfMonth());
		System.out.println("First day of month = "+day);
		day = localDate.with(TemporalAdjusters.firstDayOfNextMonth());
		System.out.println("First day of next month = "+day);
	}
}

Java Program to adjust LocalDate to first Day of Month

java8

import java.time.LocalDate;
import java.time.Month;
import java.time.temporal.TemporalAdjusters;
public class Demo {
	public static void main(String[] args) {
		LocalDate localDate = LocalDate.of(2019, Month.APRIL, 10);
		System.out.println("Current Date = "+localDate);
		System.out.println("Current Month = "+localDate.getMonth());
		LocalDate day = localDate.with(TemporalAdjusters.firstDayOfMonth());
		System.out.println("First day of month = "+day);
	}
}

Java Program to get first Friday in a month

java8

import java.time.DayOfWeek;
import java.time.LocalDate;
import java.time.Month;
import java.time.temporal.TemporalAdjusters;
public class Demo {
	public static void main(String[] args) {
		LocalDate date = LocalDate.of(2019, Month.APRIL, 1);
		System.out.println("Current date = "+date);
		LocalDate firstFriday = date.with(TemporalAdjusters.firstInMonth(DayOfWeek.FRIDAY));
		System.out.println("First Friday date = "+firstFriday);
	}
}

Java Program to get day of week for the last day of each month in 2019

java8

import java.time.DayOfWeek;
import java.time.LocalDate;
import java.time.Month;
import java.time.temporal.TemporalAdjusters;
import java.util.ArrayList;
import java.util.List;
public class Demo {
		public static void main(String[] argv) {
		List<DayOfWeek>dayOfWeek = new ArrayList<>();
		for (Month m: Month.values()) {
			DayOfWeek days = LocalDate.now().withYear(2019).with(m).with(TemporalAdjusters.lastDayOfMonth()).getDayOfWeek();
		dayOfWeek.add(days);
		}
		System.out.println("Last day of each month in 2019 = "+dayOfWeek);
	}
}

Java Program to get display name for Day of Week in different locale

java8

import java.time.DayOfWeek;
import java.time.format.TextStyle;
import java.util.Locale;
public class Demo {
public static void main(String[] args) {
	    Locale locale = Locale.getDefault();
	    Locale locale1 = Locale.CANADA;
	    System.out.printf("%s%n", DayOfWeek.THURSDAY.minus(2).getDisplayName(TextStyle.SHORT, locale));
	    System.out.printf("%s%n", DayOfWeek.THURSDAY.minus(2).getDisplayName(TextStyle.SHORT, locale1));
       Locale locale2 = Locale.FRENCH;
	    System.out.printf("%s%n", DayOfWeek.SUNDAY.minus(10).getDisplayName(TextStyle.SHORT, locale2));
	}
}

Java Program to get the reverse of the NavigableSet

java8

import java.util.NavigableSet;
import java.util.TreeSet;
public class Demo {
	public static void main(String[] args) {
		NavigableSet<String> set = new TreeSet<>();
		set.add("ABC");
		set.add("DEF");
		set.add("GHI");
		set.add("JKL");
		set.add("MNO");
		set.add("PQR");
		set.add("STU");
		NavigableSet<String>reverse = set.descendingSet();
		System.out.println("NavigableSet = " + set);
		System.out.println("NavigableSet (Reverse) = " + reverse);
	}
}

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