JDK 1.8中forEach的用法

Java中遍历容器主要用for，在JDK 1.8中提供了forEach方法，源码如下：

/**
 * Performs the given action for each element of the {@code Iterable}
 * until all elements have been processed or the action throws an
 * exception.  Unless otherwise specified by the implementing class,
 * actions are performed in the order of iteration (if an iteration order
 * is specified).  Exceptions thrown by the action are relayed to the
 * caller.
 *
 * @implSpec
 * 
The default implementation behaves as if:
 * 
{@code
 *     for (T t : this)
 *         action.accept(t);
 * }
 *
 * @param action The action to be performed for each element
 * @throws NullPointerException if the specified action is null
 * @since 1.8
 */

default void forEach(Consumersuper T> action) {
    Objects.requireNonNull(action);
    for (T t : this) {
        action.accept(t);
    }
}

用法：

public class ForEach{
    public static void  main(String[] args) {
        List list = new ArrayList();
        list.add("first");
        list.add("second");
        list.add("third");
        list.add("four");
        list.add("five");

        list.forEach((num)->System.out.println(num));
        return;
    }
}

输出：

first
second
third
four
five