java-8带有参数的谓词

Question

For java8 in action example :: https://github.com/java8/Java8InAction/blob/master/src/main/java/lambdasinaction/chap1/FilteringApples.java

 public static boolean isGreenApple(Apple apple), 
 public static boolean isHeavyApple(Apple apple) {

I want to add a similar method eg

public static boolean isAppleOfColor(Apple apple, String color)

And i want to access it using same pattern ::

 List<Apple> colorApples = filterApples(inventory, FilteringApples::isAppleOfColor("red"));

But I can't pass arguments in FilteringApples::isAppleOfColor("red").

So far I have achieved this using following :

public static Predicate<Apple> colourMatches( String color) {
    return p->color.equals(p.getColor());
}

and then calling

  List<Apple> colorApples = filterApples(inventory, (Apple a)->a.colourMatchesOnApple("red"));
    System.out.println(colorApples);

This works. But is there a way I can use the "referred" parameterized methods like FilteringApples::isAppleOfColor("red").

thanks

EDIT

Thanks All, I just realized in JLS 15.13 : https://docs.oracle.com/javase/specs/jls/se8/html/jls-15.html#jls-15.13 as following text:

It is not possible to specify a particular signature to be matched, for example, Arrays::sort(int[]). Instead, the functional interface provides argument types that are used as input to the overload resolution algorithm (§15.12.2). This should satisfy the vast majority of use cases; when the rare need arises for more precise control, a lambda expression can be used.

Answer 1

Method reference cannot capture additional variables.

What you can do is

List<Apple> colorApples = filterApples(inventory, a -> isAppleOfColor(a, "red"));

which you will note is shorter.

Note: I would avoid using a static method esp when the first argument is a type you are writing. Much better to add

// added to Apple
public boolean isColor(String color)

and you can call

List<Apple> colorApples = filterApples(inventory, a -> a.isColor("red"));

which is likely to be the same as

List<Apple> colorApples = inventory.stream()
                                   .filter(a -> a.isColor("red"))
                                   .collect(toList());