Skip to content
Snippets Groups Projects
Commit cee323ca authored by Stuart Marks's avatar Stuart Marks
Browse files

Add new set of lambda & method reference exercises

parent 5e60fa85
No related branches found
No related tags found
No related merge requests found
Hide whitespace changes
Inline Side-by-side
LambdaLab/test/exercises/A_LambdasAndMethodReferences.java 0 → 100644
+ 217
− 0
View file @ cee323ca
package exercises;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.function.BiFunction;
import java.util.function.Consumer;
import java.util.function.DoublePredicate;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.function.Supplier;
import org.junit.Ignore;
import org.junit.Test;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;
/**
* This set of exercises is about lambdas and method references.
* You will write a lambda or method reference corresponding to
* each of several different functional interfaces. Each exercise
* is named after the functional interface intended to be used
* as the solution.
*/
public class A_LambdasAndMethodReferences {
@Test @Ignore
public void a01predicate() {
// TODO: write a lambda expression that is a predicate
// that tests whether a string is longer than four characters.
Predicate<String> pred = null;
assertTrue(pred.test("abcde"));
assertFalse(pred.test("abcd"));
}
@Test @Ignore
public void a02predicate() {
// TODO: write a lambda expression that is a predicate
// that tests whether a string is empty
Predicate<String> pred = null;
assertTrue(pred.test(""));
assertFalse(pred.test("a"));
}
@Test @Ignore
public void a03predicate() {
// TODO: write a method reference that is a predicate
// that tests whether a string is empty
Predicate<String> pred = null;
assertTrue(pred.test(""));
assertFalse(pred.test("a"));
}
@Test @Ignore
public void a04function() {
// TODO: write a lambda expression that wraps the given
// string in parentheses.
Function<String, String> func = null;
assertEquals("(abc)", func.apply("abc"));
}
@Test @Ignore
public void a05function() {
// TODO: write a lambda expression that converts the
// given string to upper case.
Function<String, String> func = null;
assertEquals("ABC", func.apply("abc"));
}
@Test @Ignore
public void a06function() {
// TODO: write a method reference that converts the
// given string to upper case.
Function<String, String> func = null;
assertEquals("ABC", func.apply("abc"));
}
@Test @Ignore
public void a07consumer() {
// TODO: write a lambda expression that appends the
// string "abc" to the given StringBuilder.
Consumer<StringBuilder> cons = null;
StringBuilder sb = new StringBuilder("xyz");
cons.accept(sb);
assertEquals("xyzabc", sb.toString());
}
@Test @Ignore
public void a08consumer() {
// TODO: write a lambda expression that clears the given list.
Consumer<StringBuilder> cons = null;
List<String> list = new ArrayList<>(Arrays.asList("a", "b", "c"));
cons.accept(list);
assertTrue(list.isEmpty());
}
@Test @Ignore
public void a09consumer() {
// TODO: write a method reference that clears the given list.
Consumer<StringBuilder> cons = null;
List<String> list = new ArrayList<>(Arrays.asList("a", "b", "c"));
cons.accept(list);
assertTrue(list.isEmpty());
}
@Test @Ignore
public void a10supplier() {
// TODO: write a lambda expression that returns a new StringBuilder
// containing the string "abc".
Supplier<StringBuilder> sup = () -> new StringBuilder("abc");
assertEquals("abc", sup.get().toString());
}
@Test @Ignore
public void a11supplier() {
// TODO: write a lambda expression that returns a new, empty StringBuilder
Supplier<StringBuilder> sup = null;
assertEquals("", sup.get().toString());
}
@Test @Ignore
public void a12supplier() {
// TODO: write a method reference that returns a new, empty StringBuilder
Supplier<StringBuilder> sup = null;
assertEquals("", sup.get().toString());
}
@Test @Ignore
public void a13doublepredicate() {
// TODO: write a lambda expression that tests whether a double value
// is greater than 10.0.
DoublePredicate pred = d -> d > 10.0;
assertTrue(pred.test(15.0));
assertFalse(pred.test(5.0));
}
@Test @Ignore
public void a14doublepredicate() {
// TODO: write a lambda expression that tests whether a double value
// is finite.
DoublePredicate pred = d -> Double.isFinite(d);
assertTrue(pred.test(0.0));
assertFalse(pred.test(Double.POSITIVE_INFINITY));
}
@Test @Ignore
public void a15doublepredicate() {
// TODO: write a method reference that tests whether a double value
// is finite.
DoublePredicate pred = Double::isFinite;
assertTrue(pred.test(0.0));
assertFalse(pred.test(Double.POSITIVE_INFINITY));
}
@Test @Ignore
public void a16bifunction() {
// TODO: write a lambda expression, given two strings, returns the result
// of concatenating the first, followed by the second, followed by the
// first again.
BiFunction<String, String, String> bifunc = (s1, s2) -> s1 + s2 + s1;
assertEquals("abcdefabc", bifunc.apply("abc", "def"));
}
@Test @Ignore
public void a17bifunction() {
// TODO: write a lambda expression that returns the index of
// the first occurrence the second string within the first string,
// or -1 if the second string doesn't occur within the first string.
BiFunction<String, String, Integer> bifunc = (s1, s2) -> s1.indexOf(s2);
assertTrue(bifunc.apply("abcdefghi", "def") == 3);
assertTrue(bifunc.apply("abcdefghi", "xyz") == -1);
}
@Test @Ignore
public void a18bifunction() {
// TODO: write a method reference that returns the index of
// the first occurrence the second string within the first string,
// or -1 if the second string doesn't occur within the first string.
BiFunction<String, String, Integer> bifunc = String::indexOf;
assertTrue(bifunc.apply("abcdefghi", "def") == 3);
assertTrue(bifunc.apply("abcdefghi", "xyz") == -1);
}
@Test @Ignore
public void a19runnable() {
StringBuilder sb = new StringBuilder("abc");
String suffix = "xyz";
// TODO: write a lambda expression that appends the 'suffix'
// variable (a String) to the sb variable (a StringBuilder).
Runnable r = () -> sb.append(suffix);
r.run();
r.run();
r.run();
assertEquals("abcxyzxyzxyz", sb.toString());
}
}
LambdaLab/test/solutions/A_LambdasAndMethodReferences.java 0 → 100644
+ 250
− 0
View file @ cee323ca
package solutions;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.function.BiFunction;
import java.util.function.Consumer;
import java.util.function.DoublePredicate;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.function.Supplier;
import org.junit.Ignore;
import org.junit.Test;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;
/**
* This set of exercises is about lambdas and method references.
* You will write a lambda or method reference corresponding to
* each of several different functional interfaces. Each exercise
* is named after the functional interface intended to be used
* as the solution.
*/
public class A_LambdasAndMethodReferences {
@Test
public void a01predicate() {
// TODO: write a lambda expression that is a predicate
// that tests whether a string is longer than four characters.
//UNCOMMENT//Predicate<String> pred = null;
//BEGINREMOVE
Predicate<String> pred = s -> s.length() > 4;
//ENDREMOVE
assertTrue(pred.test("abcde"));
assertFalse(pred.test("abcd"));
}
@Test
public void a02predicate() {
// TODO: write a lambda expression that is a predicate
// that tests whether a string is empty
//UNCOMMENT//Predicate<String> pred = null;
//BEGINREMOVE
Predicate<String> pred = s -> s.isEmpty();
//ENDREMOVE
assertTrue(pred.test(""));
assertFalse(pred.test("a"));
}
@Test
public void a03predicate() {
// TODO: write a method reference that is a predicate
// that tests whether a string is empty
//UNCOMMENT//Predicate<String> pred = null;
//BEGINREMOVE
Predicate<String> pred = String::isEmpty;
//ENDREMOVE
assertTrue(pred.test(""));
assertFalse(pred.test("a"));
}
@Test
public void a04function() {
// TODO: write a lambda expression that wraps the given
// string in parentheses.
//UNCOMMENT//Function<String, String> func = null;
//BEGINREMOVE
Function<String, String> func = s -> "(" + s + ")";
//ENDREMOVE
assertEquals("(abc)", func.apply("abc"));
}
@Test
public void a05function() {
// TODO: write a lambda expression that converts the
// given string to upper case.
//UNCOMMENT//Function<String, String> func = null;
//BEGINREMOVE
Function<String, String> func = s -> s.toUpperCase();
//ENDREMOVE
assertEquals("ABC", func.apply("abc"));
}
@Test
public void a06function() {
// TODO: write a method reference that converts the
// given string to upper case.
//UNCOMMENT//Function<String, String> func = null;
//BEGINREMOVE
Function<String, String> func = String::toUpperCase;
//ENDREMOVE
assertEquals("ABC", func.apply("abc"));
}
@Test
public void a07consumer() {
// TODO: write a lambda expression that appends the
// string "abc" to the given StringBuilder.
//UNCOMMENT//Consumer<StringBuilder> cons = null;
//BEGINREMOVE
Consumer<StringBuilder> cons = sb -> sb.append("abc");
//ENDREMOVE
StringBuilder sb = new StringBuilder("xyz");
cons.accept(sb);
assertEquals("xyzabc", sb.toString());
}
@Test
public void a08consumer() {
// TODO: write a lambda expression that clears the given list.
//UNCOMMENT//Consumer<StringBuilder> cons = null;
//BEGINREMOVE
Consumer<List<String>> cons = list -> list.clear();
//ENDREMOVE
List<String> list = new ArrayList<>(Arrays.asList("a", "b", "c"));
cons.accept(list);
assertTrue(list.isEmpty());
}
@Test
public void a09consumer() {
// TODO: write a method reference that clears the given list.
//UNCOMMENT//Consumer<StringBuilder> cons = null;
//BEGINREMOVE
Consumer<List<String>> cons = List::clear;
//ENDREMOVE
List<String> list = new ArrayList<>(Arrays.asList("a", "b", "c"));
cons.accept(list);
assertTrue(list.isEmpty());
}
@Test
public void a10supplier() {
// TODO: write a lambda expression that returns a new StringBuilder
// containing the string "abc".
Supplier<StringBuilder> sup = () -> new StringBuilder("abc");
assertEquals("abc", sup.get().toString());
}
@Test
public void a11supplier() {
// TODO: write a lambda expression that returns a new, empty StringBuilder
//UNCOMMENT//Supplier<StringBuilder> sup = null;
//BEGINREMOVE
Supplier<StringBuilder> sup = () -> new StringBuilder();
//ENDREMOVE
assertEquals("", sup.get().toString());
}
@Test
public void a12supplier() {
// TODO: write a method reference that returns a new, empty StringBuilder
//UNCOMMENT//Supplier<StringBuilder> sup = null;
//BEGINREMOVE
Supplier<StringBuilder> sup = StringBuilder::new;
//ENDREMOVE
assertEquals("", sup.get().toString());
}
@Test
public void a13doublepredicate() {
// TODO: write a lambda expression that tests whether a double value
// is greater than 10.0.
DoublePredicate pred = d -> d > 10.0;
assertTrue(pred.test(15.0));
assertFalse(pred.test(5.0));
}
@Test
public void a14doublepredicate() {
// TODO: write a lambda expression that tests whether a double value
// is finite.
DoublePredicate pred = d -> Double.isFinite(d);
assertTrue(pred.test(0.0));
assertFalse(pred.test(Double.POSITIVE_INFINITY));
}
@Test
public void a15doublepredicate() {
// TODO: write a method reference that tests whether a double value
// is finite.
DoublePredicate pred = Double::isFinite;
assertTrue(pred.test(0.0));
assertFalse(pred.test(Double.POSITIVE_INFINITY));
}
@Test
public void a16bifunction() {
// TODO: write a lambda expression, given two strings, returns the result
// of concatenating the first, followed by the second, followed by the
// first again.
BiFunction<String, String, String> bifunc = (s1, s2) -> s1 + s2 + s1;
assertEquals("abcdefabc", bifunc.apply("abc", "def"));
}
@Test
public void a17bifunction() {
// TODO: write a lambda expression that returns the index of
// the first occurrence the second string within the first string,
// or -1 if the second string doesn't occur within the first string.
BiFunction<String, String, Integer> bifunc = (s1, s2) -> s1.indexOf(s2);
assertTrue(bifunc.apply("abcdefghi", "def") == 3);
assertTrue(bifunc.apply("abcdefghi", "xyz") == -1);
}
@Test
public void a18bifunction() {
// TODO: write a method reference that returns the index of
// the first occurrence the second string within the first string,
// or -1 if the second string doesn't occur within the first string.
BiFunction<String, String, Integer> bifunc = String::indexOf;
assertTrue(bifunc.apply("abcdefghi", "def") == 3);
assertTrue(bifunc.apply("abcdefghi", "xyz") == -1);
}
@Test
public void a19runnable() {
StringBuilder sb = new StringBuilder("abc");
String suffix = "xyz";
// TODO: write a lambda expression that appends the 'suffix'
// variable (a String) to the sb variable (a StringBuilder).
Runnable r = () -> sb.append(suffix);
r.run();
r.run();
r.run();
assertEquals("abcxyzxyzxyz", sb.toString());
}
}
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment