java.util.function包详解-Lambda java.util.function包详解-Lambda

您有任何问题或意见都可以在评论区回复哦，欢迎大家一起来讨论，共同学习进步 java.util.function包中有43个function interface，但是实际上只有四大类：
Consumers消费者
Supplier供应商
Functions功能
Predicates谓词
1.Consumers一个对象，BiConsumer两个对象实际都是对传入的T实体进行操作处理

public interface Consumer { public void accept(T var1); }Consumer printer = s-> System.out.println(s); //或者 Consumer printer = System.out::println; public interface BiConsumer { void accept(T var1, U var2); }

2.Supplier返回类型T的对象，没有任何入参实际是创建了T实体并返回的操作

public interface Supplier { T get(); }Supplier bankAccountSupplier = ()->new BankAccount(); //或者 Supplier bankAccountSupplier = BankAccount::new;

3.Function 实际上是对类型T实体进行相应的操作并返回类型为R的实体

public interface Function { R apply(T var1); } Function amtFunction = bankAccount -> bankAccount.getBalance(); //或者 Function amtFunction = BankAccount::getBalance;

4.Predicate 确定实体T是否满足约束，返回boolean

public interface Predicate { boolean test(T t); } Predicate test = bankAccount -> bankAccount.getBalance()>10; //自定义 Predicate p = new Predicate() { @Override public boolean test(String s) { return s.length()<20; } }; p = s -> s.length()<20; System.out.println(p.test("Hello 12321321321321312321321"));

5.还有一些其他的类型 intPredicate，intFunction，intConsumer，入参需要指定为int
以及intToDoubleFunction，入参为int，返回参数为double

public interface IntFunction { R apply(int value); } public interface LongToDoubleFunction { double applyAsDouble(long value); }

【java.util.function包详解-Lambda】可以自定义Predicate接口，标准验证以及自定义方法，静态方法等

@FunctionalInterface public interface Predicate { public boolean test(T t); public default Predicate and(Predicate other){ return t -> test(t) && other.test(t); } public default Predicate or(Predicate other){ return t -> test(t) || other.test(t); } //静态方法第一种 public static Predicate isEqualsTo(String string){ return s -> s.equals(string); } //还可以写成另一种 public static Predicate isEqualsTo(U u){ return s -> s.equals(u); } } public class Main { public static void main(String[] args) { Predicate p1 = s -> s.length()<20; Predicate p2 = s -> s.length()>5; boolean b= p1.test("Hello"); System.out.println("Hello is shorter than 20 chars is :"+b); 输出： Hello is shorter than 20 chars is :true Predicate p3 = p1.and(p2); System.out.println("p3 test 123 :"+p3.test("123")); System.out.println("p3 test 123456 :"+p3.test("123456")); System.out.println("p3 test 123456789012345678901 :"+p3.test("123456789012345678901")); 输出： p3 test 123 :false p3 test 123456 :true p3 test 123456789012345678901 :false Predicate p4 = p1.or(p2); System.out.println("p4 test 123 :"+p4.test("123")); System.out.println("p4 test 123456 :"+p4.test("123456")); System.out.println("p4 test 123456789012345678901 :"+p4.test("123456789012345678901")); 输出： p4 test 123 :true p4 test 123456 :true p4 test 123456789012345678901 :true Predicate p5 = Predicate.isEqualsTo("YES"); System.out.println("p5 test YES :"+p5.test("YES")); System.out.println("p5 test NO :"+p5.test("NO")); 输出： p5 test YES :true p5 test NO :false } }