Java 8: Interface with single method

Question

Sometime I need to make callback from one method to another:

final Integer i = 5;
final Integer j = 10;
foo("arg1", "arg2", (x, y) -> { 
    /** do sth which need this context **/ 
    bar(i + x, j - y);
})

But in such case I need to write simple interface (somewhere):

public interface someName {
    void noMatterName(Integer a, Integer c);
}

Then function foo() can call noMatterName - this is ok. But in simple cases, name of such interfaces and its function is not important. I just want to use lambda with two parameters.

Question:

Do I need to create this interface manually even if I need to make such "communication" between only two function? Does Java provide any similar interface? Or even something like this:

public interface someName1 {
    void noMatterName(Object a);
}

public interface someName2 {
    void noMatterName(Object a, Object b);
}

Community · Accepted Answer · 2020-06-20 09:12:55Z

5

You can use the Consumer<T> (if you need a single parameter), and BiConsumer<T,U> (if you need 2 parameters) functional interfaces.

Interface Consumer<T>

Represents an operation that accepts a single input argument and returns no result.

Interface BiConsumer<T,U>

Represents an operation that accepts two input arguments and returns no result.

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Sep 17, 2015 at 15:15

sstan

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