Java8四大函数式接口

@FunctionalInterface
public interface Runnable {
    public abstract void run();
}
//  foreach（消费者类型的函数式接口）

@FunctionalInterface
public interface Function<T, R> {

    /**
     * Applies this function to the given argument.
     *
     * @param t the function argument
     * @return the function result
     */
    R apply(T t);
}

// 只要是函数型接口，可以用lambda表达式简化
public static void main(String[] args) {
        Function function = new Function<String, String>() {
            @Override
            public String apply(String string) {
                return string;
            }
        };
        System.out.println(function.apply("hello"));
    }

// 简化写法
public static void main(String[] args) {
        Function<String, String> function = (str) -> {
            return str;
        };
        System.out.println(function.apply("hello"));
    }

hello

@FunctionalInterface
public interface Predicate<T> {

    /**
     * Evaluates this predicate on the given argument.
     *
     * @param t the input argument
     * @return {@code true} if the input argument matches the predicate,
     * otherwise {@code false}
     */
    boolean test(T t);
}

/**
 * 判断字符串是否为空
 * @param args
 */
public static void main(String[] args) {
    Predicate<String> predicate = (str) ->{
        return str.isEmpty();
    };
    System.out.println(predicate.test("11"));
}

false
true

@FunctionalInterface
public interface Consumer<T> {

    /**
     * Performs this operation on the given argument.
     *
     * @param t the input argument
     */
    void accept(T t);
}

/**
 * 打印字符串
 *
 * @param args
 */
public static void main(String[] args) {
    Consumer<String> consumer = str -> {
        System.out.println(str);
    };
    consumer.accept("consumer");
}

consumer

@FunctionalInterface
public interface Supplier<T> {

    /**
     * Gets a result.
     *
     * @return a result
     */
    T get();
}

/**
 * 返回固定值 1024
 *
 * @param args
 */
public static void main(String[] args) {
    Supplier<Integer> supplier = () -> {
        return 1024;
    };
    System.out.println(supplier.get());
}

1024