Java8中Stream的排序，查找和匹配的用法

排序

sorted( )---自然排序

sorted(Comparator com)---定制排序

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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;
}

@Override
public String toString() {
    return "Employee{" +
            "name='" + name + '\'' +
            ", age=" + age +
            ", salary=" + salary +
            ", status=" + status +
            '}';
}

@Override
public 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);
}

@Override
public int hashCode() {
    return Objects.hash(name, age, salary);
}

public enum Status{
    FREE,
    BUSY,
    VOCATION;
}
}

@Test
public 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

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

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)
);
@Test
public 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());
}

@Test
public 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());
}

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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

查找与匹配

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