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Exercise from second lesson (by Narek Karapetian) #166

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573396c
Exercise from second lesson (by Narek Karapetian)
Jul 4, 2017
06307d9
Remove Predicate::negate, and change operator & to &&.
Jul 5, 2017
4417b19
Change line ending.
Jul 5, 2017
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108 changes: 55 additions & 53 deletions src/test/java/lambda/part2/exercise/ArrowNotationExercise.java
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Original file line number Diff line number Diff line change
@@ -1,53 +1,55 @@
package lambda.part2.exercise;

import data.Person;
import org.junit.Test;

import java.util.function.BiFunction;
import java.util.function.BiPredicate;
import java.util.function.Function;

import static org.junit.Assert.assertEquals;

public class ArrowNotationExercise {

@Test
public void getAge() {
// Person -> Integer
final Function<Person, Integer> getAge = null; // TODO

assertEquals(Integer.valueOf(33), getAge.apply(new Person("", "", 33)));
}

@Test
public void compareAges() {
// TODO use BiPredicate
// compareAges: (Person, Person) -> boolean

throw new UnsupportedOperationException("Not implemented");
//assertEquals(true, compareAges.test(new Person("a", "b", 22), new Person("c", "d", 22)));
}

// TODO
// getFullName: Person -> String

// TODO
// ageOfPersonWithTheLongestFullName: (Person -> String) -> (Person, Person) -> int
//

@Test
public void getAgeOfPersonWithTheLongestFullName() {
// Person -> String
final Function<Person, String> getFullName = null; // TODO

// (Person, Person) -> Integer
// TODO use ageOfPersonWithTheLongestFullName(getFullName)
final BiFunction<Person, Person, Integer> ageOfPersonWithTheLongestFullName = null;

assertEquals(
Integer.valueOf(1),
ageOfPersonWithTheLongestFullName.apply(
new Person("a", "b", 2),
new Person("aa", "b", 1)));
}
}
package lambda.part2.exercise;
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This diff is unreadable. I suspect you've changed line endings.
Fix it.

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Done.


import data.Person;
import org.junit.Test;

import java.util.function.BiPredicate;
import java.util.function.Function;
import java.util.function.ToIntBiFunction;

import static org.junit.Assert.assertEquals;

public class ArrowNotationExercise {

@Test
public void getAge() {
// Person -> Integer
final Function<Person, Integer> getAge = Person::getAge;

assertEquals(Integer.valueOf(33), getAge.apply(new Person("", "", 33)));
}

@Test
public void compareAges() {
// compareAges: (Person, Person) -> boolean
BiPredicate<Person, Person> compareAges = (person, person2) -> person.getAge() == person2.getAge();

assertEquals(true, compareAges.test(new Person("a", "b", 22), new Person("c", "d", 22)));
}

// getFullName: Person -> String
public String getFullName(Person p) {
return String.format("%s %s", p.getFirstName(), p.getLastName());
}

// ageOfPersonWithTheLongestFullName: (Person -> String) -> (Person, Person) -> int
public ToIntBiFunction<Person, Person> ageOfPersonWithTheLongestFullName(Function<Person, String> fullName) {
return (p1, p2) -> fullName.apply(p1).length() > fullName.apply(p2).length() ? p1.getAge() : p2.getAge();
}

@Test
public void getAgeOfPersonWithTheLongestFullName() {
// Person -> String
final Function<Person, String> getFullName = this::getFullName;

// (Person, Person) -> Integer
final ToIntBiFunction<Person, Person> ageOfPersonWithTheLongestFullName =
ageOfPersonWithTheLongestFullName(getFullName);

assertEquals(
1,
ageOfPersonWithTheLongestFullName.applyAsInt(
new Person("a", "b", 2),
new Person("aa", "b", 1)));
}
}
36 changes: 12 additions & 24 deletions src/test/java/lambda/part2/exercise/FunctionCombinationExercise.java
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Original file line number Diff line number Diff line change
Expand Up @@ -19,22 +19,14 @@ public void personHasNotEmptyLastNameAndFirstName0() {
assertEquals(false, validate.test(new Person("a", "", 0)));
}

// TODO
// negate1: (Person -> boolean) -> (Person -> boolean)
private Predicate<Person> negate1(Predicate<Person> test) {
return p -> {
// TODO
throw new UnsupportedOperationException();
};
private Predicate<Person> negate1(Predicate<Person> predicate) {
return p -> !predicate.test(p);
}

// TODO
// validateFirstNameAndLastName: (Person -> boolean, Person -> boolean) -> (Person -> boolean)
private Predicate<Person> validateFirstNameAndLastName(Predicate<Person> t1, Predicate<Person> t2) {
return p -> {
// TODO
throw new UnsupportedOperationException();
};
return p -> t1.test(p) && t2.test(p);
}

@Test
Expand All @@ -52,29 +44,25 @@ public void personHasNotEmptyLastNameAndFirstName1() {
assertEquals(false, validate.test(new Person("a", "", 0)));
}

// TODO
// negate: (T -> boolean) -> (T -> boolean)
private <T> Predicate<T> negate(Predicate<T> test) {
// TODO
throw new UnsupportedOperationException();
private <T> Predicate<T> negate(Predicate<T> predicate) {
return t -> !predicate.test(t);
}

// TODO
// and: (T -> boolean, T -> boolean) -> (T -> boolean)
private <T> Predicate<T> and(Predicate<T> t1, Predicate<T> t2) {
// TODO
throw new UnsupportedOperationException();
return t -> t1.test(t) && t2.test(t);
}

@Test
public void personHasNotEmptyLastNameAndFirstName2() {
final Predicate<Person> hasEmptyFirstName = p -> p.getFirstName().isEmpty();
final Predicate<Person> hasEmptyLastName = p -> p.getLastName().isEmpty();

final Predicate<Person> validateFirstName = null; // TODO use negate
final Predicate<Person> validateLastName = null; // TODO use negate
final Predicate<Person> validateFirstName = negate(hasEmptyFirstName);
final Predicate<Person> validateLastName = negate(hasEmptyLastName);

final Predicate<Person> validate = null; // TODO use and
final Predicate<Person> validate = and(validateFirstName, validateLastName);

assertEquals(true, validate.test(new Person("a", "b", 0)));
assertEquals(false, validate.test(new Person("", "b", 0)));
Expand All @@ -86,10 +74,10 @@ public void personHasNotEmptyLastNameAndFirstName3() {
final Predicate<Person> hasEmptyFirstName = p -> p.getFirstName().isEmpty();
final Predicate<Person> hasEmptyLastName = p -> p.getLastName().isEmpty();

final Predicate<Person> validateFirstName = null; // TODO use Predicate::negate
final Predicate<Person> validateLastName = null; // TODO use Predicate::negate
final Predicate<Person> validateFirstName = hasEmptyFirstName.negate();
final Predicate<Person> validateLastName = hasEmptyLastName.negate();

final Predicate<Person> validate = null; // TODO use Predicate::and
final Predicate<Person> validate = and(validateFirstName, validateLastName);

assertEquals(true, validate.test(new Person("a", "b", 0)));
assertEquals(false, validate.test(new Person("", "b", 0)));
Expand Down