常用的流操作如下列出。
我們可以使用Stream <T>接口的窺探(Consumer<?super T>action)方法調(diào)試流。
IntStream,LongStream和DoubleStream還包含一個(gè)peek()方法,它接受IntConsumer,LongConsumer和DoubleConsumer作為參數(shù)。
我們可以使用帶有peek()方法的lambda表達(dá)式來記錄元素。
以下代碼使用peek()方法打印通過流管道的元素:
import java.util.stream.Stream; public class Main { public static void main(String[] args) { int sum = Stream.of(1, 2, 3, 4, 5) .peek(e -> System.out.println("Taking integer: " + e)) .filter(n -> n % 2 == 1) .peek(e -> System.out.println("Filtered integer: " + e)) .map(n -> n * n).peek(e -> System.out.println("Mapped integer: " + e)) .reduce(0, Integer::sum); System.out.println("Sum = " + sum); } }
上面的代碼生成以下結(jié)果。
forEach操作對流的每個(gè)元素執(zhí)行操作。
Stream<T>
接口包含兩種方法來執(zhí)行forEach操作:
void forEach(Consumer<? super T> action) void forEachOrdered(Consumer<? super T> action)
IntStream,LongStream和DoubleStream包含相同的方法。
forEach()方法不保證操作的順序應(yīng)用流中的每個(gè)元素。
forEachOrdered()方法按元素的順序執(zhí)行操作由流定義。
forEachOrdered()方法可能會減慢并行流中的處理速度。
以下代碼打印員工列表中的女性詳細(xì)信息:
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() .filter(Employee::isFemale) .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 dob, double income) { this.id = id; this.name = name; this.gender = gender; this.dob = dob; this.income = income; } public boolean isFemale() { return this.gender == Gender.FEMALE; } public static List<Employee> persons() { Employee p1 = new Employee(1, "Jake", Gender.MALE, LocalDate.of(1971, Month.JANUARY, 1), 2343.0); Employee p2 = new Employee(2, "Jack", Gender.MALE, LocalDate.of(1972, Month.JULY, 21), 7100.0); Employee p3 = new Employee(3, "Jane", Gender.FEMALE, LocalDate.of(1973, Month.MAY, 29), 5455.0); Employee p4 = new Employee(4, "Jode", Gender.MALE, LocalDate.of(1974, Month.OCTOBER, 16), 1800.0); Employee p5 = new Employee(5, "Jeny", Gender.FEMALE, LocalDate.of(1975, Month.DECEMBER, 13), 1234.0); Employee p6 = new Employee(6, "Jason", Gender.MALE, LocalDate.of(1976, Month.JUNE, 9), 3211.0); List<Employee> persons = Arrays.asList(p1, p2, p3, p4, p5, p6); return persons; } }
上面的代碼生成以下結(jié)果。
以下代碼顯示如何使用forEach()方法將所有女性的收入增加10%。
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) { List<Employee> persons = Employee.persons(); System.out.println("Before increasing the income: " + persons); persons.stream() .filter(Employee::isFemale) .forEach(p -> p.setIncome(p.getIncome() * 1.10)); System.out.println("After increasing the income: " + persons); } } 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 dob, double income) { this.id = id; this.name = name; this.gender = gender; this.dob = dob; this.income = income; } public Gender getGender() { return gender; } public boolean isMale() { return this.gender == Gender.MALE; } public boolean isFemale() { return this.gender == Gender.FEMALE; } public void setGender(Gender gender) { this.gender = gender; } public double getIncome() { return income; } public void setIncome(double income) { this.income = income; } public static List<Employee> persons() { Employee p1 = new Employee(1, "Jake", Gender.MALE, LocalDate.of(1971, Month.JANUARY, 1), 2343.0); Employee p2 = new Employee(2, "Jack", Gender.MALE, LocalDate.of(1972, Month.JULY, 21), 7100.0); Employee p3 = new Employee(3, "Jane", Gender.FEMALE, LocalDate.of(1973, Month.MAY, 29), 5455.0); Employee p4 = new Employee(4, "Jode", Gender.MALE, LocalDate.of(1974, Month.OCTOBER, 16), 1800.0); Employee p5 = new Employee(5, "Jeny", Gender.FEMALE, LocalDate.of(1975, Month.DECEMBER, 13), 1234.0); Employee p6 = new Employee(6, "Jason", Gender.MALE, LocalDate.of(1976, Month.JUNE, 9), 3211.0); List<Employee> persons = Arrays.asList(p1, p2, p3, p4, p5, p6); return persons; } @Override public String toString() { String str = String.format("(%s, %s, %s, %s, %.2f)\n", id, name, gender, dob, income); return str; } }
上面的代碼生成以下結(jié)果。
更多建議: