Читать книгу OCP Oracle Certified Professional Java SE 17 Developer Study Guide - Jeanne Boyarsky - Страница 55

Use the following assessment test to gauge your current level of skill in Java for the 1Z0-829. This test is designed to highlight some topics for your strengths and weaknesses so that you know which chapters you might want to read multiple times. Even if you do well on the assessment test, you should still read the book from cover to cover, as the real exams are quite challenging.

1 What is the result of executing the following code snippet?41: final int score1 = 8, score2 = 3; 42: char myScore = 7; 43: var goal = switch (myScore) { 44: default -> {if(10>score1) yield "unknown";} 45: case score1 -> "great"; 46: case 2, 4, 6 -> "good"; 47: case score2, 0 -> {"bad";} 48: }; 49: System.out.println(goal);unknowngreatgoodbadunknowngreatgoodbadExactly one line needs to be changed for the code to compile.Exactly two lines need to be changed for the code to compile.None of the above

2 What is the output of the following code snippet?int moon = 9, star = 2 + 2 * 3; float sun = star>10 ? 1 : 3; double jupiter = (sun + moon) - 1.0f; int mars = --moon <= 8 ? 2 : 3; System.out.println(sun+", "+jupiter+", "+mars);1, 11, 23.0, 11.0, 21.0, 11.0, 33.0, 13.0, 33.0f, 12, 2The code does not compile because one of the assignments requires an explicit numeric cast.

3 Which changes, when made independently, guarantee the following code snippet prints 100 at runtime? (Choose all that apply.)List<Integer> data = new ArrayList<>(); IntStream.range(0,100).parallel().forEach(s -> data.add(s)); System.out.println(data.size());Change data to an instance variable and mark it volatile.Remove parallel() in the stream operation.Change forEach() to forEachOrdered() in the stream operation.Change parallel() to serial() in the stream operation.Wrap the lambda body with a synchronized block.The code snippet will always print 100 as is.

4 What is the output of this code?20: Predicate<String> empty = String::isEmpty; 21: Predicate<String> notEmpty = empty.negate(); 22: 23: var result = Stream.generate(() -> "") 24: .filter(notEmpty) 25: .collect(Collectors.groupingBy(k -> k)) 26: .entrySet() 27: .stream() 28: .map(Entry::getValue) 29: .flatMap(Collection::stream) 30: .collect(Collectors.partitioningBy(notEmpty)); 31: System.out.println(result);It outputs {}.It outputs {false=[], true=[]}.The code does not compile.The code does not terminate.

5 What is the result of the following program?1: public class MathFunctions { 2: public static void addToInt(int x, int amountToAdd) { 3: x = x + amountToAdd; 4: } 5: public static void main(String[] args) { 6: var a = 15; 7: var b = 10; 8: MathFunctions.addToInt(a, b); 9: System.out.println(a); } }101525Compiler error on line 3Compiler error on line 8None of the above

6 Suppose that we have the following property files and code. What values are printed on lines 8 and 9, respectively?Penguin.properties name=Billy age=1 Penguin_de.properties name=Chilly age=4 Penguin_en.properties name=Willy 5: Locale fr = new Locale("fr"); 6: Locale.setDefault(new Locale("en", "US")); 7: var b = ResourceBundle.getBundle("Penguin", fr); 8: System.out.println(b.getString("name")); 9: System.out.println(b.getString("age"));Billy and 1Billy and nullWilly and 1Willy and nullChilly and nullThe code does not compile.

7 What is guaranteed to be printed by the following code? (Choose all that apply.)int[] array = {6,9,8}; System.out.println("B" + Arrays.binarySearch(array,9)); System.out.println("C" + Arrays.compare(array, new int[] {6, 9, 8})); System.out.println("M" + Arrays.mismatch(array, new int[] {6, 9, 8}));B1B2C-1C0M-1M0The code does not compile.

8 Which functional interfaces complete the following code, presuming variable r exists? (Choose all that apply.)6: ______ x = r.negate(); 7: ______ y = () -> System.out.println(); 8: ______ z = (a, b) -> a - b;BinaryPredicate<Integer, Integer>Comparable<Integer>Comparator<Integer>Consumer<Integer>Predicate<Integer>RunnableRunnable<Integer>

9 Suppose you have a module named com.vet. Where could you place the following module-info.java file to create a valid module?public module com.vet { exports com.vet; }At the same level as the com folderAt the same level as the vet folderInside the vet folderNone of the above

10 What is the output of the following program? (Choose all that apply.)1: interface HasTail { private int getTailLength(); } 2: abstract class Puma implements HasTail { 3: String getTailLength() { return "4"; } 4: } 5: public class Cougar implements HasTail { 6: public static void main(String[] args) { 7: var puma = new Puma() {}; 8: System.out.println(puma.getTailLength()); 9: } 10: public int getTailLength(int length) { return 2; } 11: }24The code will not compile because of line 1.The code will not compile because of line 3.The code will not compile because of line 5.The code will not compile because of line 7.The code will not compile because of line 10.The output cannot be determined from the code provided.

11 Which lines in Tadpole.java give a compiler error? (Choose all that apply.)// Frog.java 1: package animal; 2: public class Frog { 3: protected void ribbit() { } 4: void jump() { } 5: } // Tadpole.java 1: package other; 2: import animal.*; 3: public class Tadpole extends Frog { 4: public static void main(String[] args) { 5: Tadpole t = new Tadpole(); 6: t.ribbit(); 7: t.jump(); 8: Frog f = new Tadpole(); 9: f.ribbit(); 10: f.jump(); 11: } }Line 5Line 6Line 7Line 8Line 9Line 10All of the lines compile.

12 Which of the following can fill in the blanks in order to make this code compile?__________ a = __________.getConnection( url, userName, password); __________ b = a.prepareStatement(sql); __________ c = b.executeQuery(); if (c.next()) System.out.println(c.getString(1));Connection, Driver, PreparedStatement, ResultSetConnection, DriverManager, PreparedStatement, ResultSetConnection, DataSource, PreparedStatement, ResultSetDriver, Connection, PreparedStatement, ResultSetDriverManager, Connection, PreparedStatement, ResultSetDataSource, Connection, PreparedStatement, ResultSet

13 Which of the following statements can fill in the blank to make the code compile successfully? (Choose all that apply.)Set<? extends RuntimeException> mySet = new _________ ();HashSet<? extends RuntimeException>HashSet<Exception>TreeSet<RuntimeException>TreeSet<NullPointerException>None of the above

14 Assume that birds.dat exists, is accessible, and contains data for a Bird object. What is the result of executing the following code? (Choose all that apply.)1: import java.io.*; 2: public class Bird { 3: private String name; 4: private transient Integer age; 5: 6: // Getters/setters omitted 7: 8: public static void main(String[] args) { 9: try(var is = new ObjectInputStream( 10: new BufferedInputStream( 11: new FileInputStream("birds.dat")))) { 12: Bird b = is.readObject(); 13: System.out.println(b.age); 14: } } }It compiles and prints 0 at runtime.It compiles and prints null at runtime.It compiles and prints a number at runtime.The code will not compile because of lines 9–11.The code will not compile because of line 12.It compiles but throws an exception at runtime.

15 Which of the following are valid instance members of a class? (Choose all that apply.)var var = 3;Var case = new Var();void var() {}int Var() { var _ = 7; return _;}String new = "var";var var() { return null; }

16 Which is true if the table is empty before this code is run? (Choose all that apply.)var sql = "INSERT INTO people VALUES(?, ?, ?)"; conn.setAutoCommit(false); try (var ps = conn.prepareStatement(sql, ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE)) { ps.setInt(1, 1); ps.setString(2, "Joslyn"); ps.setString(3, "NY"); ps.executeUpdate(); Savepoint sp = conn.setSavepoint(); ps.setInt(1, 2); ps.setString(2, "Kara"); ps.executeUpdate(); conn._________________; }If the blank line contains rollback(), there are no rows in the table.If the blank line contains rollback(), there is one row in the table.If the blank line contains rollback(sp), there are no rows in the table.If the blank line contains rollback(sp), there is one row in the table.The code does not compile.The code throws an exception because the second update does not set all the parameters.

17 Which is true if the contents of path1 start with the text Howdy? (Choose two.)System.out.println(Files.mismatch(path1,path2));If path2 doesn't exist, the code prints -1.If path2 doesn't exist, the code prints 0.If path2 doesn't exist, the code throws an exception.If the contents of path2 start with Hello, the code prints -1.If the contents of path2 start with Hello, the code prints 0.If the contents of path2 start with Hello, the code prints 1.

18 Which of the following types can be inserted into the blank to allow the program to compile successfully? (Choose all that apply.)1: import java.util.*; 2: final class Amphibian {} 3: abstract class Tadpole extends Amphibian {} 4: public class FindAllTadpoles { 5: public static void main(String… args) { 6: var tadpoles = new ArrayList<Tadpole>(); 7: for (var amphibian : tadpoles) { 8: ___________ tadpole = amphibian; 9: } } }List<Tadpole>BooleanAmphibianTadpoleObjectNone of the above

19 What is the result of compiling and executing the following program?1: public class FeedingSchedule { 2: public static void main(String[] args) { 3: var x = 5; 4: var j = 0; 5: OUTER: for (var i = 0; i < 3;) 6: INNER: do { 7: i++; 8: x++; 9: if (x> 10) break INNER; 10: x += 4; 11: j++; 12: } while (j <= 2); 13: System.out.println(x); 14: } }10111217The code will not compile because of line 5.The code will not compile because of line 6.

20 When printed, which String gives the same value as this text block?var pooh = """ "Oh, bother." -Pooh """.indent(1); System.out.print(pooh);"\n\"Oh, bother.\" -Pooh\n""\n \"Oh, bother.\" -Pooh\n"" \"Oh, bother.\" -Pooh\n""\n\"Oh, bother.\" -Pooh""\n \"Oh, bother.\" -Pooh"" \"Oh, bother.\" -Pooh"None of the above

21 A(n) _________________ module always contains a module-info.java file, while a(n) _________________ module always exports all its packages to other modules.automatic, namedautomatic, unnamednamed, automaticnamed, unnamedunnamed, automaticunnamed, namedNone of the above

22 What is the result of the following code?22: var treeMap = new TreeMap<Character, Integer>(); 23: treeMap.put('k', 1); 24: treeMap.put('k', 2); 25: treeMap.put('m', 3); 26: treeMap.put('M', 4); 27: treeMap.replaceAll((k, v) -> v + v); 28: treeMap.keySet() 29: .forEach(k -> System.out.print(treeMap.get(k)));26846824688268468246None of the above

23 Which of the following lines can fill in the blank to print true? (Choose all that apply.)10: public static void main(String[] args) { 11: System.out.println(test(____________________________)); 12: } 13: private static boolean test(Function<Integer, Boolean> b) { 14: return b.apply(5); 15: }i::equals(5)i -> {i == 5;}(i) -> i == 5(int i) -> i == 5(int i) -> {return i == 5;}(i) -> {return i == 5;}

24 How many times is the word true printed?var s1 = "Java"; var s2 = "Java"; var s3 = s1.indent(1).strip(); var s4 = s3.intern(); var sb1 = new StringBuilder(); sb1.append("Ja").append("va"); System.out.println(s1 == s2); System.out.println(s1.equals(s2)); System.out.println(s1 == s3); System.out.println(s1 == s4); System.out.println(sb1.toString() == s1); System.out.println(sb1.toString().equals(s1));OnceTwiceThree timesFour timesFive timesThe code does not compile.

25 What is the output of the following program?1: class Deer { 2: public Deer() {System.out.print("Deer");} 3: public Deer(int age) {System.out.print("DeerAge");} 4: protected boolean hasHorns() { return false; } 5: } 6: public class Reindeer extends Deer { 7: public Reindeer(int age) {System.out.print("Reindeer");} 8: public boolean hasHorns() { return true; } 9: public static void main(String[] args) { 10: Deer deer = new Reindeer(5); 11: System.out.println("," + deer.hasHorns()); 12: } }ReindeerDeer,falseDeerAgeReindeer,trueDeerReindeer,trueDeerReindeer,falseReindeerDeer,trueDeerAgeReindeer,falseThe code will not compile because of line 4.The code will not compile because of line 12.

26 Which of the following are true? (Choose all that apply.)private static void magic(Stream<Integer> s) { Optional o = s .filter(x -> x < 5) .limit(3) .max((x, y) -> x-y); System.out.println(o.get()); }magic(Stream.empty()); runs infinitely.magic(Stream.empty()); throws an exception.magic(Stream.iterate(1, x -> x++)); runs infinitely.magic(Stream.iterate(1, x -> x++)); throws an exception.magic(Stream.of(5, 10)); runs infinitely.magic(Stream.of(5, 10)); throws an exception.The method does not compile.

27 Assuming the following declarations are top-level types declared in the same file, which successfully compile? (Choose all that apply.)record Music() { final int score = 10; } record Song(String lyrics) { Song { this.lyrics = lyrics + "Hello World"; } } sealed class Dance {} record March() { @Override String toString() { return null; } } class Ballet extends Dance {}MusicSongDanceMarchBalletNone of them compile.

28 Which of the following expressions compile without error? (Choose all that apply.)int monday = 3 + 2.0;double tuesday = 5_6L;boolean wednesday = 1 > 2 ? !true;short thursday = (short)Integer.MAX_VALUE;long friday = 8.0L;var saturday = 2_.0;None of the above

29 What is the result of executing the following application?final var cb = new CyclicBarrier(3, () -> System.out.println("Clean!")); // u1 ExecutorService service = Executors.newSingleThreadExecutor(); try { IntStream.generate(() -> 1) .limit(12) .parallel() .forEach(i -> service.submit(() -> cb.await())); // u2 } finally { service.shutdown(); }It outputs Clean! at least once.It outputs Clean! exactly four times.The code will not compile because of line u1.The code will not compile because of line u2.It compiles but throws an exception at runtime.It compiles but waits forever at runtime.

30 Which statement about the following method is true?5: public static void main(String… unused) { 6: System.out.print("a"); 7: try (StringBuilder reader = new StringBuilder()) { 8: System.out.print("b"); 9: throw new IllegalArgumentException(); 10: } catch (Exception e || RuntimeException e) { 11: System.out.print("c"); 12: throw new FileNotFoundException(); 13: } finally { 14: System.out.print("d"); 15: } }It compiles and prints abc.It compiles and prints abd.It compiles and prints abcd.One line contains a compiler error.Two lines contain a compiler error.Three lines contain a compiler error.It compiles but prints an exception at runtime.