Java8 Supplier接口和Consumer接口原理解析
Supplier接口
package java.util.function;
/**
* Represents a supplier of results.
*
* <p>There is no requirement that a new or distinct result be returned each
* time the supplier is invoked.
*
* <p>This is a <a href="package-summary.html" rel="external nofollow" rel="external nofollow" >functional interface</a>
* whose functional method is {@link #get()}.
*
* @param <T> the type of results supplied by this supplier
*
* @since 1.8
*/
@FunctionalInterface
public interface Supplier<T> {
/**
* Gets a result.
*
* @return a result
*/
T get();
}
supplier接口只有一个抽象方法get(),通过get方法产生一个T类型实例。
实例：
package me.yanand;
import java.util.function.Supplier;
public class TestSupplier {
public static void main(String[] args) {
Supplier<Apple> appleSupplier = Apple::new;
System.out.println("--------");
appleSupplier.get();
}
}
class Apple{
public Apple() {
System.out.println("创建实例");
}
}
Consumer接口
package java.util.function;
import java.util.Objects;
/**
* Represents an operation that accepts a single input argument and returns no
* result. Unlike most other functional interfaces, {@code Consumer} is expected
* to operate via side-effects.
*
* <p>This is a <a href="package-summary.html" rel="external nofollow" rel="external nofollow" >functional interface</a>
* whose functional method is {@link #accept(Object)}.
*
* @param <T> the type of the input to the operation
*
* @since 1.8
*/
@FunctionalInterface
public interface Consumer<T> {
/**
* Performs this operation on the given argument.
*
* @param t the input argument
*/
void accept(T t);
/**
* Returns a composed {@code Consumer} that performs, in sequence, this
* operation followed by the {@code after} operation. If performing either
* operation throws an exception, it is relayed to the caller of the
* composed operation. If performing this operation throws an exception,
* the {@code after} operation will not be performed.
*
* @param after the operation to perform after this operation
* @return a composed {@code Consumer} that performs in sequence this
* operation followed by the {@code after} operation
* @throws NullPointerException if {@code after} is null
*/
default Consumer<T> andThen(Consumer<? super T> after) {
Objects.requireNonNull(after);
return (T t) -> { accept(t); after.accept(t); };
}
}
一个抽象方法accept(T t)定义了要执行的具体操作；注意看andThen方法，接收Consumer<? super T>类型参数，返回一个lambda表达式，此表达式定义了新的执行过程，先执行当前Consumer实例的accept方法，再执行入参传进来的Consumer实例的accept方法，这两个accept方法接收都是相同的入参t。
实例：
package me.yanand;
import java.util.function.Consumer;
public class TestConsumer {
public static void main(String[] args) {
Consumer<Integer> consumer = (t) -> {
System.out.println(t*3);
};
Consumer<Integer> consumerAfter = (s) -> {
System.out.println("之后执行："+s);
};
consumer.andThen(consumerAfter).accept(5);
}
}
以上是 Java8 Supplier接口和Consumer接口原理解析 的全部内容， 来源链接： utcz.com/z/354535.html
