Java8中Stream的排序，查和匹配的⽤法Java8中Stream的排序，查和匹配的⽤法
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;
}
@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 &&
Doublepare(employee.salary, salary) == 0 &&
Objects.equals(name, employee.name);
}
@Override
java streampublic int hashCode() {
return Objects.hash(name, age, salary);
}
public enum Status{
FREE,
BUSY,
VOCATION;
}
}
@Test
public void test1(){
List<String> 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()){
Name()Name());
}else{
return Age(), e2.getAge());
}
}).forEach(System.out::println);
}
查与匹配
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
0. min---返回流中最⼩值
List<Employee> 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<Employee> op = employees.stream()
.sorted((e1, e2) -> Salary(), e2.getSalary()))            .findFirst();
System.out.());
//findAny---返回当前流中的任意元素
Optional<Employee> op2 = employees.stream()
.
filter((e) -> e.getStatus().equals(Employee.Status.FREE))
.findAny();
System.out.());
}
@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<Employee> op1 = employees.stream()
.max((e1, e2) -> Salary(), e2.getSalary()));    System.out.());
//min---返回流中最⼩值
Optional<Double> op2 = employees.stream()
.map(Employee::getSalary)
.min(Double::compare);
System.out.());
}

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