JAVA chapter16. 스트림과 병렬처리. 16.5 매핑(flatMapXXX(), mapXXX(), asXXXStream(), boxed())

JAVA chapter16. 스트림과 병렬처리. 

16.5 매핑(flatMapXXX(), mapXXX(), asXXXStream(), boxed())

16.5.1 flatMapXXX() 메소드

package sec05.stream_mapping;
 
import java.util.Arrays;
import java.util.List;
import java.util.stream.IntStream;
 
public class FlatMapExample {
    public static void main(String[] args) {
        List<String> inputList1 = Arrays.asList("java8 lambda", "stream mapping");
        inputList1.stream()
            .flatMap(data -> Arrays.stream(data.split(" ")))
            .forEach(word -> System.out.println(word));
        
        System.out.println();
        
        List<String> inputList2 = Arrays.asList("10, 20, 30", "40, 50, 60");
        inputList2.stream()
            .flatMapToInt(data -> {
                String[] strArr = data.split(",");
                int[] intArr = new int[strArr.length];
                for(int i=0; i<strArr.length; i++) {
                    intArr[i] = Integer.parseInt(strArr[i].trim());
                }
                return Arrays.stream(intArr);
            })
            .forEach(number -> System.out.println(number));
    }
}

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package sec05.stream_mapping;   public class Student {     private String name;     private int score;          public Student(String name, int score) {         this.name = name;         this.score = score;     }       public String getName() { return name; }     public int getScore() { return score; } } Colored by Color Scripter

cs

package sec05.stream_mapping;
 
import java.util.Arrays;
import java.util.List;
 
public class MapExample {
    public static void main(String[] args) {
        List<Student> studentList = Arrays.asList(
                new Student("홍길동", 10),
                new Student("신용권", 20),
                new Student("유미선", 30)
        );
            
        studentList.stream()
            .mapToInt(Student :: getScore) // .mapToInt(s->s.getScore())
            .forEach(score -> System.out.println(score));
    }
}

package sec05.stream_mapping;
 
import java.util.Arrays;
import java.util.stream.IntStream;
 
public class AsDoubleStreamAndBoxedExample {
    public static void main(String[] args) {
        int[] intArray = { 1, 2, 3, 4, 5};
        
        IntStream intStream = Arrays.stream(intArray);
        intStream
            .asDoubleStream()
            .forEach(d -> System.out.println(d));
            
        System.out.println();
        
        intStream = Arrays.stream(intArray);
        intStream
            .boxed()
            .forEach(obj -> System.out.println(obj.intValue()));
    }
}