Java8中Stream的排序，查找和匹配的用法

Java8中Stream的排序，查找和匹配的用法

排序

1. sorted( )---自然排序

2. sorted(Comparator com)---定制排序

   public class Employee {private String name;private Integer age;private Double salary;private Status status;public Employee() {    super();}public  Employee(Integer age){    this.age = age;}public Employee(String name, Integer age, Double salary) {    super();    this.name = name;    this.age = age;    this.salary = salary;}public Employee(String name, Integer age, Double salary, Status status) {    this.name = name;    this.age = age;    this.salary = salary;    this.status = status;}public String getName() {    return name;}public void setName(String name) {    this.name = name;}public int getAge() {    return age;}public void setAge(Integer age) {    this.age = age;}public double getSalary() {    return salary;}public void setSalary(Double salary) {    this.salary = salary;}public Status getStatus() {    return status;}public void setStatus(Status status) {    this.status = status;}@Overridepublic String toString() {    return "Employee{" +            "name='" + name + '\'' +            ", age=" + age +            ", salary=" + salary +            ", status=" + status +            '}';}@Overridepublic boolean equals(Object o) {    if (this == o) return true;    if (o == null || getClass() != o.getClass()) return false;    Employee employee = (Employee) o;    return age == employee.age &&            Double.compare(employee.salary, salary) == 0 &&            Objects.equals(name, employee.name);}@Overridepublic int hashCode() {    return Objects.hash(name, age, salary);}public enum Status{    FREE,    BUSY,    VOCATION;}}

   @Testpublic void test1(){    List list = Arrays.asList("ccc", "aaa", "bbb", "ddd", "eee");    //自然排序    list.stream()        .sorted()        .forEach(System.out::println);    System.out.println("------------------------------");    //定制排序    employees.stream()             .sorted((e1, e2) -> {                 if (e1.getAge() == e2.getAge()){                     return e1.getName().compareTo(e2.getName());                 }else{                     return Integer.compare(e1.getAge(), e2.getAge());                 }             }).forEach(System.out::println);}

   查找与匹配

3. allMatch---检查是否匹配所有元素
4. anyMatch---检查是否至少匹配一个元素
5. noneMatch---检查是否没有匹配所有元素
6. findFirst---返回第一个元素
7. findAny---返回当前流中的任意元素
8. count---返回流中元素的总个数
9. max---返回流中最大值

10. min---返回流中最小值

    List employees = Arrays.asList(        new Employee("张三", 18 ,9999.99, Employee.Status.FREE),        new Employee("李四", 38, 5555.99, Employee.Status.BUSY),        new Employee("王五", 50, 6666.66, Employee.Status.VOCATION),        new Employee("赵六", 16, 3333.33, Employee.Status.FREE),        new Employee("田七", 8, 7777.77, Employee.Status.BUSY));@Testpublic void test2(){    //allMatch---检查是否匹配所有元素    boolean b1 = employees.stream()            .allMatch((e) -> e.getStatus().equals(Employee.Status.BUSY));    System.out.println(b1);    //anyMatch---检查是否至少匹配一个元素    boolean b2 = employees.stream()             .anyMatch((e) -> e.getStatus().equals(Employee.Status.BUSY));    System.out.println(b2);    //noneMatch---检查是否没有匹配所有元素    boolean b3 = employees.stream()             .noneMatch((e) -> e.getStatus().equals(Employee.Status.BUSY));    System.out.println(b3);    //findFirst---返回第一个元素    Optional op = employees.stream()             .sorted((e1, e2) -> Double.compare(e1.getSalary(), e2.getSalary()))             .findFirst();    System.out.println(op.get());    //findAny---返回当前流中的任意元素    Optional op2 = employees.stream()             .filter((e) -> e.getStatus().equals(Employee.Status.FREE))             .findAny();    System.out.println(op2.get());}@Testpublic void test3(){    //count---返回流中元素的总个数    Long count = employees.stream()             .count();    System.out.println(count);    //max---返回流中最大值    Optional op1 = employees.stream()            .max((e1, e2) -> Double.compare(e1.getSalary(), e2.getSalary()));    System.out.println(op1.get());    //min---返回流中最小值    Optional op2 = employees.stream()            .map(Employee::getSalary)            .min(Double::compare);    System.out.println(op2.get());}