Java 流映射.pdfVIP

Java 流映射 Java流 - Java流映射 映射操作对每个元素应⽤函数以产⽣另⼀流。 输⼊和输出流中的元素数量是相同的。 该操作 修改输⼊流的元素。 您可以使⽤Stream T接⼜的以下⽅法之⼀对流应⽤地图操作： R StreamR map(Function? super T,? extends R mapper) DoubleStream mapToDouble(ToDoubleFunction? super T mapper) IntStream mapToInt(ToIntFunction? super T mapper) LongStream mapToLong(ToLongFunction? super T mapper) IntStream ，LongStream和DoubleStream也定义了映射函数。⽀持对IntStream进⾏映射 操作的⽅法如下： IntStream map(Int naryOperator mapper) DoubleStream mapToDouble(IntToDoubleFunction mapper) LongStream mapToLong(IntToLongFunction mapper) Stream mapToObj(IntFunction? extends mapper) 以下代码显⽰如何使⽤map()将IntStream 中的元素映射到其正⽅形，并在标准输出上打 印映射流。 import java.util.stream.IntStream; public class Main { public static void main(String[] args) { IntStream.rangeClosed(1, 5) .map(n - n * n) .forEach(System.out::println); } } 上⾯的代码⽣成以下结果。 例2 以下代码将员⼯流映射到其名称，并打印映射流。 import java.time.LocalDate; import java.time.Month; import java.util.Arrays; import java.util.List; public class Main { public static void main(String[] args) { Employee.persons() .stream() .map(Employee::getName) .forEach(System.out::println); } } class Employee { public static enum Gender { MALE, FEMALE } private long id; private String name; private Gender gender; private LocalDate dob; private double income; public Employee(long id, String name, Gender gender, LocalDate d double income) { this.id = id; = name; this.gender = gender; this.dob = dob; this.income = income; } public long getId() { return id; } public void setId(long id) { this.id = id; } public String getName() { return name; } public void setName(String name) { = name; } public Gender getGender() { return gender; } public boolean isMale() { return this.gender == Gender.MALE; } public boolean i