Java Stream

1 create stream

1.1 Stream.of(val1, val2, val3….)

import java.util.*;
import java.util.stream.*;
public class Demo {
    public static void main(String[] args) {
        Stream<Integer> stream=Stream.of(1,2,3,4);
        stream.forEach(System.out::println);
    }
}

1.2 Stream.of(arrayOfElements)

import java.util.stream.*;
public class Demo {
    public static void main(String[] args) {
        Stream<Integer> stream=Stream.of(new Integer[] {1,2,3,4});
        stream.forEach(System.out::println);
    }
}

1.3 List.stream()

import java.util.*;
import java.util.stream.*;
public class Demo {
    public static void main(String[] args) {
        List<Integer> list=new ArrayList<Integer>();
        list.add(1);
        list.add(2);
        list.forEach(System.out::println);
    }
}

1.4 Stream.generate() 

import java.util.*;
import java.util.stream.*;
public class Demo {
    public static void main(String[] args) {
        Stream<Date> stream=Stream.generate(()->new Date());
        stream.forEach(System.out::println);
    }
}

1.5 String chars or String tokens

import java.util.*;
import java.util.stream.*;
public class Demo {
    public static void main(String[] args) {
        IntStream stream = "12345_abcdefg".chars();
        stream.forEach(p -> System.out.println(p));
         
        //OR
         
        Stream<String> stream1 = Stream.of("A$B$C".split("\\$"));
        stream1.forEach(p -> System.out.println(p));
    }
}

2 Convert streams to collections

2.1  to List – Stream.collect( Collectors.toList() )

import java.util.*;
import java.util.stream.*;
public class Demo {
    public static void main(String[] args) {

        var stream =Stream.of(1,2,3,4);
        var list=stream.collect(Collectors.toList());

    }
}

2.2  to array – Stream.toArray( EntryType[]::new )

import java.util.*;
import java.util.stream.*;
public class Demo {
    public static void main(String[] args) {

        var stream =Stream.of(1,2,3,4);
        var list=stream.toArray(Integer[]::new);

    }
}