Add Debugging Pipe

StreamExample.java

import java.util.Arrays;
import java.util.function.Function;

/**
 * Created with IntelliJ IDEA.
 * User: owner
 * Date: 13/05/06
 * Time: 14:41
 * To change this template use File | Settings | File Templates.
 */
public class StreamExample {
    public static void main(String... args){
        Arrays.asList("1", "Foo", "2", "Bar", "3")
                .stream()
                .map(debug("Before filter: "))
                .filter(str -> str.matches("\\d"))
                .map(debug("After filter: "))
                .forEach(System.out::println);
    }

    public static <T> Function<T, T> debug(String debugStr){
        return (T t) -> {
             System.out.println(debugStr + t);
             return t;
        };
    }

}

Output:

Before filter: 1
After filter: 1
1
Before filter: Foo
Before filter: 2
After filter: 2
2
Before filter: Bar
Before filter: 3
After filter: 3
3