Java 8: Tree Stream of parent tree nodes

Legacy.java

package java8tree;

import java8tree.data.FooBar;
import java8tree.data.TreeNode;

public class Legacy {

	public FooBar findFooBar(TreeNode selection) {
		FooBar foobar = null;
		if (istFooBar(selection.getParentPath())) {
			foobar = (FooBar) selection.getParentPath().getLastPathComponent().getModel();
		} else if (istFooBar(selection.getParentPath().getParentPath())) {
			foobar = (FooBar) selection.getParentPath().getParentPath().getLastPathComponent().getModel();
		} else if (istFooBar(selection.getParentPath().getParentPath().getParentPath())) {
			foobar = (FooBar) selection.getParentPath().getParentPath().getParentPath().getLastPathComponent().getModel();
		}
		return foobar;
	}

	private boolean istFooBar(TreeNode parentPath) {
		return parentPath.getLastPathComponent().getModel() instanceof FooBar;
	}

}

LegacyToJava7.java

package java8tree;

import java8tree.data.FooBar;
import java8tree.data.Model;
import java8tree.data.TreeNode;

public class LegacyToJava7 {

	public FooBar findFooBar(TreeNode selection) {
		for (TreeNode current = selection; current != null; current = current.getParentPath()) {
			Model lastPath = extractLastpath(current);
			if (lastPath instanceof FooBar) {
				return (FooBar) lastPath;
			}
		}
		return null;
	}

	private static Model extractLastpath(TreeNode parentPath) {
		return parentPath.getLastPathComponent().getModel();
	}

}

LegacyToJava8.java

package java8tree;

import static java.util.stream.Stream.concat;
import static java.util.stream.Stream.empty;

import java.util.Objects;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.stream.Stream;

import java8tree.data.FooBar;
import java8tree.data.PathComponent;
import java8tree.data.TreeNode;

public class LegacyToJava8Generic2 {

	public FooBar findFooBar(TreeNode selection) {
		// alternative: (POFooBar) ... instead of .map(POFooBar.class::cast)
		return streamOf(selection, TreeNode::getParentPath) //
				.map(TreeNode::getLastPathComponent) //
				.map(PathComponent::getModel) //
				.filter(FooBar.class::isInstance) //
				.map(FooBar.class::cast) //
				.findFirst().orElse(null);
	}

	private static <T> Stream<T> streamOf(T t, Function<T, T> function) {
		return streamOf(t, function, Objects::isNull);
	}

	public static <T> Stream<T> streamOf(T t, Function<T, T> f, Predicate<T> p) {
		return p.test(t) ? empty() : concat(Stream.of(t), Stream.of(t).flatMap(n -> streamOf(f.apply(n), f, p)));
	}

}

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