#Java - Code Snippets for '#Java 8'

#Java - Code Snippets for '#Java 8' - 23 code snippet(s) found

Sample 1. Calculate square of a number using Lambda Expression

public interface Calc {

    int square(int value);

}



public static void main(String[] args){

    Calc calc = (int val) -> val * val;

    System.out.println(calc.square(5));

}

_{Like Feedback lambda Expression java 8}

Sample 2. Write a Program that gets a set of numbers , filters out the non prime numbers , calculate the factorial of each prime number and then finds the average of all factorials using Lambda expressions

public class BuggyBread1 {

   

   public static void main(String args[]) {

      

      // Declare and Initialize the Collection

      Set<Integer> intSet = new HashSet<Integer>();



      // Add Elements

      intSet.add(1);

      intSet.add(2);

      intSet.add(3);

      intSet.add(4);

      intSet.add(5);



      double averageOfNonPrimeFactorials = intSet.stream().filter(p->checkIfPrime(p)).collect(Collectors.averagingInt(p->calculateFactorial(p)));

      

      System.out.println(averageOfNonPrimeFactorials );

   }

   

   static private boolean checkIfPrime(int num){

      for(int count=2;count < num;count++){

         if(num % count == 0){

            return false;

         }

      }

      return true;

   }

   

   static private int calculateFactorial(int num){

      int factorial = 1;

      for(int count=num;count > 0;count--){

         factorial = factorial * count;

      }

      return factorial;

   }

}

_{Like Feedback java 8 lambda expressions lambda filter Collectors factorial prime number}

Sample 3. Interface Default Methods ( Base Class Definition has precedence over Interface Default Method if both are being extended and implemented and have common method definition )

HelloJava8Base 



public class HelloJava8Base {

     public void defaultMethod() {

         System.out.println("Default Method Base Class Implementation");

     }

}



DefaultMethodInterface 



public interface DefaultMethodInterface {

     default public void defaultMethod() {

         System.out.println("Default Method Interface Implementation");

     }

}



HelloJava8



public class HelloJava8 extends HelloJava8Base implements DefaultMethodInterface,DefaultMethodInterface2 {

   public static void main(String[] args){

       DefaultMethodInterface dmi = new HelloJava8();

       dmi.defaultMethod(); // Prints "Default Method Base Class Implementation"

    }

}

_{Like Feedback interface default methods java 8 interfaces}

Sample 4. Get the Calendar Type from the abstract chronology

AbstractChronology abstractChrono = ThaiBuddhistChronology.INSTANCE;

System.out.println(abstractChrono.getCalendarType()); // Will print buddhist

_{Like Feedback AbstractChronology java 8 AbstractChronology.getCalendarType}

Sample 5. Display Elements of a List using Java 8 Consumer

List myList = new ArrayList();

      

myList.add("A");

myList.add("B");

myList.add("C");



myList.forEach(System.out::println);

_{Like Feedback Print elements of a list java 8 consumer foreach list arraylist collections}

Sample 6. Interface Default Methods

public interface DefaultMethodInterface {

    default public void defaultMethod(){

       System.out.println("DefaultMethodInterface");        

    }

}



public interface DefaultMethodInterface2 {          

        default public void defaultMethod(){

               System.out.println("DefaultMethodInterface2");        

        }

}



public class HelloJava8 implements DefaultMethodInterface,DefaultMethodInterface2 {

   public static void main(String[] args){   

           DefaultMethodInterface defMethIn = new HelloJava8();

           defMethIn.defaultMethod();

    }



   public void defaultMethod(){

       System.out.println("HelloJava8"); 

   }

}

_{Like Feedback interface default methods interfaces java 8}

Sample 7. ArrayList of Optional Integers

List<Optional<Integer>> intList = new ArrayList<Optional<Integer>>();



// Add Elements



intList.add(Optional.empty());

intList.add(Optional.of(2));

intList.add(Optional.of(3));

intList.add(Optional.of(4));

_{Like Feedback optional java 8 list arraylist list of optional integers arraylist of optional java.util.Optional}

Sample 8. Get Date using ZonedDateTime and LocalDateTime

ZonedDateTime zonedDatetime = ZonedDateTime.of(201, 1, 31, 14, 35, 12, 123, ZoneId.of("UTC-11"));

System.out.println(zonedDatetime.get(ChronoField.HOUR_OF_DAY));



LocalDateTime localDateTime = LocalDateTime.of(2015, 03, 10, 13, 36);

System.out.println(localDateTime);



ZonedDateTime zonedDatetime2 = ZonedDateTime.now(ZoneId.of("merica/Chicago"));

System.out.println(zonedDatetime2);



ZonedDateTime zonedDatetime3 = ZonedDateTime.of(localDateTime, ZoneId.of("America/Chicago"));

System.out.println(zonedDatetime3);

_{Like Feedback ZonedDateTime LocalDateTime ZonedDateTime.of LocalDateTime.of ZonedDateTime.now ZoneId ZoneId.of java.time.ZonedDateTime java.time java 8}

Sample 9. Internal Implementation of ChronoField

public enum ChronoField implements TemporalField {

    NANO_OF_SECOND("NanoOfSecond", NANOS, SECONDS, ValueRange.of(0, 999_999_999)),

    NANO_OF_DAY("NanoOfDay", NANOS, DAYS, ValueRange.of(0, 86400L * 1000_000_000L - 1)),

    MICRO_OF_SECOND("MicroOfSecond", MICROS, SECONDS, ValueRange.of(0, 999_999)),

    MICRO_OF_DAY("MicroOfDay", MICROS, DAYS, ValueRange.of(0, 86400L * 1000_000L - 1)),

    MILLI_OF_SECOND("MilliOfSecond", MILLIS, SECONDS, ValueRange.of(0, 999)),

    MILLI_OF_DAY("MilliOfDay", MILLIS, DAYS, ValueRange.of(0, 86400L * 1000L - 1)),

    SECOND_OF_MINUTE("SecondOfMinute", SECONDS, MINUTES, ValueRange.of(0, 59), "second"),

    SECOND_OF_DAY("SecondOfDay", SECONDS, DAYS, ValueRange.of(0, 86400L - 1)),

    MINUTE_OF_HOUR("MinuteOfHour", MINUTES, HOURS, ValueRange.of(0, 59), "minute"),

    MINUTE_OF_DAY("MinuteOfDay", MINUTES, DAYS, ValueRange.of(0, (24 * 60) - 1)),

    HOUR_OF_AMPM("HourOfAmPm", HOURS, HALF_DAYS, ValueRange.of(0, 11)),

    CLOCK_HOUR_OF_AMPM("ClockHourOfAmPm", HOURS, HALF_DAYS, ValueRange.of(1, 12)),

    HOUR_OF_DAY("HourOfDay", HOURS, DAYS, ValueRange.of(0, 23), "hour"),

    CLOCK_HOUR_OF_DAY("ClockHourOfDay", HOURS, DAYS, ValueRange.of(1, 24)),

    AMPM_OF_DAY("AmPmOfDay", HALF_DAYS, DAYS, ValueRange.of(0, 1), "dayperiod"),

    DAY_OF_WEEK("DayOfWeek", DAYS, WEEKS, ValueRange.of(1, 7), "weekday"),

    ALIGNED_DAY_OF_WEEK_IN_MONTH("AlignedDayOfWeekInMonth", DAYS, WEEKS, ValueRange.of(1, 7)),

    ALIGNED_DAY_OF_WEEK_IN_YEAR("AlignedDayOfWeekInYear", DAYS, WEEKS, ValueRange.of(1, 7)),

    DAY_OF_MONTH("DayOfMonth", DAYS, MONTHS, ValueRange.of(1, 28, 31), "day"),

    DAY_OF_YEAR("DayOfYear", DAYS, YEARS, ValueRange.of(1, 365, 366)),

    EPOCH_DAY("EpochDay", DAYS, FOREVER, ValueRange.of((long) (Year.MIN_VALUE * 365.25), (long) (Year.MAX_VALUE * 365.25))),

    ALIGNED_WEEK_OF_MONTH("AlignedWeekOfMonth", WEEKS, MONTHS, ValueRange.of(1, 4, 5)),

    ALIGNED_WEEK_OF_YEAR("AlignedWeekOfYear", WEEKS, YEARS, ValueRange.of(1, 53)),

    MONTH_OF_YEAR("MonthOfYear", MONTHS, YEARS, ValueRange.of(1, 12), "month"),

    PROLEPTIC_MONTH("ProlepticMonth", MONTHS, FOREVER, ValueRange.of(Year.MIN_VALUE * 12L, Year.MAX_VALUE * 12L + 11)),

    YEAR_OF_ERA("YearOfEra", YEARS, FOREVER, ValueRange.of(1, Year.MAX_VALUE, Year.MAX_VALUE + 1)),

    YEAR("Year", YEARS, FOREVER, ValueRange.of(Year.MIN_VALUE, Year.MAX_VALUE), "year"),

    ERA("Era", ERAS, FOREVER, ValueRange.of(0, 1), "era"),

    INSTANT_SECONDS("InstantSeconds", SECONDS, FOREVER, ValueRange.of(Long.MIN_VALUE, Long.MAX_VALUE)),

    OFFSET_SECONDS("OffsetSeconds", SECONDS, FOREVER, ValueRange.of(-18 * 3600, 18 * 3600));



    private final String name;

    private final TemporalUnit baseUnit;

    private final TemporalUnit rangeUnit;

    private final ValueRange range;

    private final String displayNameKey;



    private ChronoField(String name, TemporalUnit baseUnit, TemporalUnit rangeUnit, ValueRange range) {

        this.name = name;

        this.baseUnit = baseUnit;

        this.rangeUnit = rangeUnit;

        this.range = range;

        this.displayNameKey = null;

    }



    private ChronoField(String name, TemporalUnit baseUnit, TemporalUnit rangeUnit,

            ValueRange range, String displayNameKey) {

        this.name = name;

        this.baseUnit = baseUnit;

        this.rangeUnit = rangeUnit;

        this.range = range;

        this.displayNameKey = displayNameKey;

    }



    @Override

    public String getDisplayName(Locale locale) {

        Objects.requireNonNull(locale, "locale");

        if (displayNameKey == null) {

            return name;

        }



        LocaleResources lr = LocaleProviderAdapter.getResourceBundleBased()

                                    .getLocaleResources(locale);

        ResourceBundle rb = lr.getJavaTimeFormatData();

        String key = "field." + displayNameKey;

        return rb.containsKey(key) ? rb.getString(key) : name;

    }



    @Override

    public TemporalUnit getBaseUnit() {

        return baseUnit;

    }



    @Override

    public TemporalUnit getRangeUnit() {

        return rangeUnit;

    }



    @Override

    public ValueRange range() {

        return range;

    }



    @Override

    public boolean isDateBased() {

        return ordinal() >= DAY_OF_WEEK.ordinal() && ordinal() <= ERA.ordinal();

    }



    @Override

    public boolean isTimeBased() {

        return ordinal() < DAY_OF_WEEK.ordinal();

    }



    public long checkValidValue(long value) {

        return range().checkValidValue(value, this);

    }



    public int checkValidIntValue(long value) {

        return range().checkValidIntValue(value, this);

    }



    @Override

    public boolean isSupportedBy(TemporalAccessor temporal) {

        return temporal.isSupported(this);

    }



    @Override

    public ValueRange rangeRefinedBy(TemporalAccessor temporal) {

        return temporal.range(this);

    }



    @Override

    public long getFrom(TemporalAccessor temporal) {

        return temporal.getLong(this);

    }



    @SuppressWarnings("unchecked")

    @Override

    public <R extends Temporal> R adjustInto(R temporal, long newValue) {

        return (R) temporal.with(this, newValue);

    }



    @Override

    public String toString() {

        return name;

    }



}

_{Like Feedback chronofield temporalfield java 8 java.time.temporal.TemporalField}

Sample 10. Today's Date as per Hijrah Chronology

AbstractChronology abstractChrono = HijrahChronology.INSTANCE;

System.out.println(abstractChrono.dateNow());

_{Like Feedback Hijrah Date Hijrah Calendar Hijrah Chronology HijrahChronology java 8 HijrahChronology.INSTANCE AbstractChronology AbstractChronology.datenow}

Sample 11. Today's Date as per Japanese Chronology

AbstractChronology abstractChrono = JapaneseChronology.INSTANCE;

System.out.println(abstractChrono.dateNow());

_{Like Feedback Japanese Chronology JapaneseChronology java 8 JapaneseChronology.INSTANCE AbstractChronology AbstractChronology.datenow}

Sample 12. Todays Date as per Minguo Chronology

AbstractChronology abstractChrono = MinguoChronology.INSTANCE;

System.out.println(abstractChrono.dateNow());

_{Like Feedback Minguo Chronology MinguoChronology java 8 MinguoChronology.INSTANCE AbstractChronology AbstractChronology.datenow}

Sample 13. Todays Date as per ThaiBuddhistChronology

AbstractChronology abstractChrono = ThaiBuddhistChronology.INSTANCE;



System.out.println(abstractChrono.dateNow());

_{Like Feedback ThaiBuddhist Chronology ThaiBuddhistChronology java 8 ThaiBuddhistChronology.INSTANCE AbstractChronology AbstractChronology.datenow}

Sample 14. Get 6 months before today as per JapaneseChronology

AbstractChronology abstractChrono = JapaneseChronology.INSTANCE;

System.out.println(abstractChrono.dateNow().minus(6, ChronoUnit.MONTHS));

_{Like Feedback AbstractChronology JapaneseChronology ChronoUnit java 8}

Sample 15. Filtering objects using google.common.base.Predicate

static Collection<Employee> employeesGreaterThan30(Collection<Employee> employees) {

    return filter(employees, new Predicate<Employee>() {

      @Override

      public boolean apply(Employee employee) {

        return employee.getAge() > 30;

      }

  });

}

_{Like Feedback predicate google.common.base.Predicate filter objects alternate for predicate before java 8 collections google guava}

Sample 16. Java 8 Map Merge Example ( Map.merge )

Map<String,String> intMap = new HashMap<String,String>();

strMap.put("Key1","Value1");

strMap.put("Key2", "Value2");    

String str = strMap.merge("Key1","Value56",(v1,v2)->v1.substring(3).concat(v2));

System.out.println(str); // prints ue1Value56

System.out.println(strMap); // prints {Key2=Value2, Key1=ue1Value56}

_{Like Feedback java 8 map.merge map merge hashmap collections}

Sample 17. Java 8 MapMerge

Map<String,String> strMap = new HashMap<String,String>();

strMap.put("Key1","Value1");

strMap.put("Key2", "Value2");    

String str = strMap.merge("Key4","Value56",(v1,v2)->v1.substring(3).concat(v2));

System.out.println(str); // prints Value56

System.out.println(strMap); // prints {Key2=Value2, Key1=Value1, Key4=Value56}

_{Like Feedback java 8 map.merge map merge hashmap collections}

Sample 18. Use java.time.format.DateTimeFormatter to Parse date in the format YYYYMMDD+HHmmss

DateTimeFormatter dateTimeFormatter = new DateTimeFormatterBuilder()

          .parseCaseInsensitive()

          .appendValue(YEAR, 4)

          .appendValue(MONTH_OF_YEAR, 2)

          .appendValue(DAY_OF_MONTH, 2)

          .appendOffset("+HHMMss", "Z")

          .toFormatter();



TemporalAccessor temporal = null;



try {

           temporal = dateTimeFormatter.parse("2016101+235700");

           System.out.println(temporal.toString()); // prints {OffsetSeconds=86220},ISO resolved to 2016-01-01

} catch (DateTimeParseException ex){

           System.out.println("Error parsing date");

}

_{Like Feedback DateTimeFormatter Parse Date in Java 8 Parse date using DateTimeFormatter and DateTimeFormatterBuilder}

Sample 19. Count elements of a collection matching a Predicate using Apache Commons IterableUtils

List<String> list = new ArrayList();

list.add("Washington");

list.add("Nevada");

list.add("California");

list.add("New York");

list.add("New Jersey");



// <String> long org.apache.commons.collections4.IterableUtils.countMatches(Iterable<String> input, Predicate<? super String> predicate)

      

System.out.println(IterableUtils.countMatches(list, p->((String)p).startsWith("N")));

_{Like Feedback Apache Commons IterableUtils Apache Commons Predicate Java 8 Count elements of a collection java8}

Sample 20. Concatenate two Streams

public static IntStream concat(IntStream a, IntStream b) {

        Objects.requireNonNull(a);

        Objects.requireNonNull(b);



        Spliterator.OfInt split = new Streams.ConcatSpliterator.OfInt(

                a.spliterator(), b.spliterator());

        IntStream stream = StreamSupport.intStream(split, a.isParallel() || b.isParallel());

        return stream.onClose(Streams.composedClose(a, b));

    }

_{Like Feedback Concatenate two Streams java 8 java8}

Sample 21. Usage of Java 8 Consumer interface

Consumer<String> consumer = s->{

   System.out.println(s);

};



consumer.accept("BuggyBread"); // prints BuggyBread

_{Like Feedback Java 8 Consumer Consumer interface}

Sample 22. Usage of java.util.function.BiPredicate

BiPredicate<String, String> predicate = (s1, s2) -> (s1.equals(s2));



System.out.println(predicate.test("BUGGY", "BREAD"));

_{Like Feedback BiPredicate Java 8 BiPredicate}

Sample 23. Averaging Group By using Java 8

<Collection_Reference>.stream().collect(Collectors.groupingBy(<Class_Name>::<Method_to_get_group_by_element>,

               Collectors.averagingDouble(<Class_Name>::<Method_to_get_element_to_perform_averaging_on>)));



Example -



Get Dept and it's average Salary



list..stream().collect(Collectors.groupingBy(Employee::getDept,

               Collectors.averagingDouble(Employee::getSalary)));

_{Like Feedback java 8}

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