Consumer Interface is another Built-In Functional Interface of java.util.function package of Java 8. The consumer interface consumes the object and doesn’t return any object. it has only one abstract method called accept(). Along with this, it has one more default method called andThen()
void accept(T t) // abstract method
default Consumer<T> andThen(Consumer<? super T> after)) // default method
Example for Consumer Interface
public class ConsumerExample
{
public static void main(String[] args) {
Consumer<String> msg = a -> System.out.println(a);
msg.accept("Hello World");
}
}
Output
Hello World
andThen() method of Consumer Interface
andThen() method is a default method of Consumer Function Interface. andThen() method accepts a consumer interface as a parameter called after which to be applied after the current one.
Below is the example to square each number and print of a list:
public class ConsumerExample
{
public static void main(String[] args) {
//Multiply by 2 each Integer element
Consumer<List<Integer>> doubleValue = a -> {
for(int i=0; i<a.size();i++)
a.set(i,2*a.get(i));
};
//Print Each element of List
Consumer<List<Integer>> printValue = a ->{
a.stream().forEach(p->System.out.println(p));
};
List<Integer> values = new ArrayList<>(Arrays.asList(3,4,5));
doubleValue.andThen(printValue).accept(values);
}
}
Output
6
8
10
Conclusion
In this article, we have seen consumer interfaces with some examples.
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