在Java8中,Consumer是一个函数式接口,它只接受一个参数,没有返回值。
Consumer.java
@FunctionalInterface
public interface Consumer<T> {
void accept(T t);
}
实例1:基本用法
下面的程序会把变量x打印到屏幕上:
Java8Consumer1.java
package cc.myexample.java8;
import java.util.function.Consumer;
public class Java8Consumer1 {
public static void main(String[] args) {
Consumer<String> print = x -> System.out.println(x);
print.accept("java"); // java
}
}
输出
java
实例2:模拟forEach
Java8Consumer2.java
package cc.myexample.java8;
import java.util.Arrays;
import java.util.List;
import java.util.function.Consumer;
public class Java8Consumer2 {
public static void main(String[] args) {
List<Integer> list = Arrays.asList(1, 2, 3, 4, 5);
// 通过变量的方式传递
Consumer<Integer> consumer = (Integer x) -> System.out.println(x);
forEach(list, consumer);
// 或通过lambda的方式传递
forEach(list, (Integer x) -> System.out.println(x));
}
static <T> void forEach(List<T> list, Consumer<T> consumer) {
for (T t : list) {
consumer.accept(t);
}
}
}
输出
1
2
3
4
5
1
2
3
4
5
我们对上面的程序进行一些改动,让它打印字符串的长度:
Java8Consumer3.java
package cc.myexample.java8;
import java.util.Arrays;
import java.util.List;
import java.util.function.Consumer;
public class Java8Consumer3 {
public static void main(String[] args) {
List<String> list = Arrays.asList("a", "ab", "abc");
forEach(list, (String x) -> System.out.println(x.length()));
}
static <T> void forEach(List<T> list, Consumer<T> consumer) {
for (T t : list) {
consumer.accept(t);
}
}
}
输出
1
2
3