JDK1.8增加了一个Consumer接口，现在就来探究一下。
后记
后记为啥要放最前面？因为懒得拖到最下面啊，O(∩_∩)O哈哈哈~
除了这个支持泛型的 Consumer 接口，又发现了三个很类似的接口
DoubleConsumer、IntConsumer、LongConsumer
这三个接口只接收对应类型的值，即Double、Int、Long
另外还有接收两个泛型参数的 BiConsumer 接口
其也有三个变形接口：ObjDoubleConsumer、ObjIntConsumer、ObjLongConsumer
这三个变形接口第一个参数支持泛型，第二个参数分别支持Double、Int、Long
值得注意的是这三个变形接口没有 andThen 方法
源码
/**
* 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">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); };
}
}
翻译
/**
* 表示接受单个输入参数并不返回结果的操作。
* 和大多数函数式接口不同，Consumer接口预计将通过副作用进行操作。
*
* 这是一个函数式接口，其函数式方法是accept。
*
* @param <T> 操作的输入类型
*
* @since 1.8
*/
@FunctionalInterface
public interface Consumer<T> {
/**
* 在给定的参数上执行此操作.
*
* @param t 输入的参数
*/
void accept(T t);
/**
* 返回一个有序的Consumer操作组合, 本操作执行之后执行after操作。
* 如果任意操作执行时抛出异常，则将异常反馈到操作组合的调用方。
* 如果本操作执行时抛出异常，则不会执行after操作。
*
* @param after 本操作之后执行的操作
* @return 一个有序的操作组合，本操作执行之后执行after操作
* @throws NullPointerException 如果after操作为null则抛空指针异常
*/
default Consumer<T> andThen(Consumer<? super T> after) {
Objects.requireNonNull(after);
return (T t) -> { accept(t); after.accept(t); };
}
}
摘要
- Consumer接口是函数式接口，其accept方法没有返回值
- Consumer接口通过副作用进行操作，我理解的就是在原来对象上进行更改（不知道对不对，😓，没有找到靠谱的资料）
实例
定义一个对象：
public class Student {
private int id;
private String name;
private int age;
public Student(int id, String name, int age) {
this.id = id;
this.name = name;
this.age = age;
}
@Override
public String toString() {
return "Student [id=" + id + ", name=" + name + ", age=" + age + "]";
}
public void setId(int id) {
this.id = id;
}
public void setName(String name) {
this.name = name;
}
public void setAge(int age) {
this.age = age;
} }
实例1：
Student student = new Student(1, "lin", 20);
System.out.println(student.toString());
Consumer<Student> c1 = s -> s.setName("chen");
c1.accept(student);
System.out.println(student.toString());
输出结果为：
Student [id=1, name=lin, age=20]
Student [id=1, name=chen, age=20]
实例2：
Student student = new Student(1, "lin", 20);
System.out.println(student.toString());
Consumer<Student> c1 = s -> s.setId(2);
Consumer<Student> c2 = s -> s.setName("chen");
Consumer<Student> c3 = s -> s.setAge(18);
c3.andThen(c2).andThen(c1).accept(student);
System.out.println(student.toString());
输出结果为：
Student [id=1, name=lin, age=20]
Student [id=2, name=chen, age=18]