lambda表达式，java双冒号（::）示例详解

 1 public class Test {
 2 
 3     // 实例对象引用实例方法
 4     Supplier supplier1 = "lowerCase"::toUpperCase;
 5     Supplier supplier1_1 = () -> "lowerCase".toUpperCase();
 6 
 7     // 类引用(无参)构造函数
 8     Supplier supplier2 = String::new;
 9     Supplier supplier2_1 = () -> new String();
10 
11     // 类引用(有参）构造函数
12     Function function1 = String::new;
13     Function function1_1 = (String str) -> new String(str);
14 
15     // 类引用实例方法，入参为传入实例对象，入参、出参同类型
16     Function function2 = String::toUpperCase;
17     Function function2_1 = (String str) -> str.toUpperCase();
18 
19     // Predicate可理解为特殊的Function
20 
21     Person person = new Person();
22     // 须为无参静态方法
23     Supplier supplierBln = Person::isTest;
24     Supplier supplierBln_1 = () -> Person.isTest();
25 
26     // 实例对象调用实例方法
27     Supplier supplierStr = person::getName;
28     Supplier supplierStr_1 = () -> person.getName();
29 
30     // 无参构造函数
31     Supplier supplierPerson = Person::new;
32     Supplier supplierPerson_1 = () -> new Person();
33 
34     // 有参构造函数
35     BiFunction biFunction = Person::new;
36     BiFunction biFunction_1 = (name, gender) -> new Person(name, gender);
37 
38     // 类名调用实例方法，入参为传入实例对象
39     Function functionP = Person::toOpposite;
40     Function functionP_1 = person -> person.toOpposite();
41 
42     Consumer consumer = System.out::println;
43     Consumer consumer_1 = (String str) -> System.out.println(str);;
44 
45     public static void main(String[] args) {
46         List list = Arrays.asList("1", "2", "3");
47         boolean bl = list.stream().anyMatch("1"::equals);
48         List retval = list.stream().collect(Collectors.toCollection(LinkedList::new));
49 
50         List persons = Arrays.asList(new Person(10, "Jack", "M"));
51         Person person = new Person(20, "Lily", "F");
52         persons.stream().filter(Person::isMale).filter(person::isUnder).collect(Collectors.toCollection(ArrayList::new));
53     }
54 }

 1 public class Person {
 2     int age;
 3     String name;
 4     String gender;
 5 
 6     public Person() {
 7     }
 8 
 9     public Person(String name) {
10         this.name = name;
11     }
12 
13     public Person(String name, String gender) {
14         this.name = name;
15         this.gender = gender;
16     }
17 
18     public Person(int age, String name, String gender) {
19         this.age = age;
20         this.name = name;
21         this.gender = gender;
22     }
23 
24     public String getName() {
25         return this.name;
26     }
27 
28     public Person toOpposite() {
29         if (gender.charAt(0) == ‘M‘)
30             gender = "F";
31         else
32             gender = "M";
33         return this;
34     }
35 
36     public static boolean isTest() {
37         return true;
38     }
39 
40     public boolean isUnder(Person person) {
41         return person.age > this.age;
42     }
43 
44     public boolean isMale() {
45         return gender.equals("M");
46     }
47 }