[OCPJP]Java SE 8 Programmer II Certification Exam | 1Z0-809 덤프/DUMP 문제#1~20

NEW QUESTION 1 Given the code fragment:

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public static void main(String[] args) throws IOException {   BufferedReader brCopy = null;   try (BufferedReader br = new BufferedReader(new FileReader("employee.txt"))) { // line n1     br.lines().forEach(c ->System.out.println(c));     brCopy = br; //line n2   }   brCopy.ready(); //line n3; }

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Assume that the ready method of the BufferedReader, when called on a closed BufferedReader, throws an exception, and employee.txt is accessible and contains valid text.
What is the result?
A. A compilation error occurs at line n3.
B. A compilation error occurs at line n1.
C. A compilation error occurs at line n2.
D. The code prints the content of the employee.txt file and throws an exception at line n3.

Answer: D

Explanation: br이 이미 try 문에서 close()되었으므로 참조하는 brCopy에서 ready를 쓸수없음.

NEW QUESTION 2 What is the result?

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BiPredicate<String, String> bp = (s1, s2) -> s1.contains("SG") && s2.contains("Java"); BiFunction<String, String, Integer> bf = (String s1, String s2) -> {     int fee = 0;     if (bp.test(s1, s2)){         fee = 100;     }     return fee; }; int fee1 = bf.apply("D101SG","Java Programming"); System.out.println(fee1);

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A. A compilation error occurs at line 7.
B. 100
C. A compilation error occurs at line 8.
D. A compilation error occurs at line 15.
Answer: B

Explanation: BiPredicates는 서로 다른 타입의 2개의 인자를 받아 boolean을 리턴, BiFunction은 서로 다른 타입의 2개의 인재를 받아 또다른 타입으로 반환하는 함수.

NEW QUESTION 3 Given the code fragment:
Which code fragment, when inserted at line 7, enables printing 100?

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IntConsumer consumer = e -> System.out.println(e); Integer value = 90; /*Insert code fragment here*/ consumer.accept(result);

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A. Function<Integer> funRef = e –> e + 10;
Integer result = funRef.apply(value);
B. IntFunction funRef = e –> e + 10;
Integer result = funRef.apply (10);
C. ToIntFunction<Integer> funRef = e –> e + 10;
int result = funRef.applyAsInt (value);
D. ToIntFunction funRef = e –> e + 10;
int result = funRef.apply (value);

Answer: A

Explanation: IntConsumer는 Int타입의 어떤 객체를 받아 void를 반환함.

NEW QUESTION 4 Given the code fragment:

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for (Course a : Course.value()){     System.out.print(a + " Fees " + a.getCost() + " "); }

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Which is the valid definition of the Course enum?


A. Option A B. Option B C. Option C D. Option D

Answer: D

Explanation: enum의 생성자는 public 접근제어자를 허용하지 않는다

NEW QUESTION 5 Given the code fragment:

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Stream<Path> files = Files.walk(Paths.get(System.getProperty("user.home"))); files.forEach(fName ->{ //line n1   try {     Path aPath = fName.toAbsolutePath(); //line n2     System.out.println(fName + ":" + Files.readAttributes(aPath, BasicFileAttributes.class).creationTime());   } catch(IOException ex) {     ex.printStackTrace();   } }); Colored by Color Scripter

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What is the result?

A. All files and directories under the home directory are listed along with their attributes.
B. A compilation error occurs at line n1.
C. The files in the home directory are listed along with their attributes.
D. A compilation error occurs at line n2.

Answer: A

※import java.util.stream.Stream;
import java.nio.file.*;
import java.nio.file.attribute.*;

NEW QUESTION 6
Which statement is true about java.time.Duration?
A. It tracks time zones.
B. It preserves daylight saving time.
C. It defines time-based values.
D. It defines date-based values.

Answer: C

Explanation: Duration deals with time. for example
LocalTime gabzTime = LocalTime.of(12, 51, 0);
LocalTime ghettoTime = gabzTime.plus(Duration.ofSeconds(45)) ;
long timeDiff = Duration.between(gabzTime, ghettoTime); // 45 seconds

NEW QUESTION 7
Given:

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class Resource implements AutoCloseable {   public void close() throws Exception {     System.out.println("Close-");   }   public void open() {     System.out.println("Open-");   } } Colored by Color Scripter

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and this code fragment:

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Resource res1 = new Resource(); try {   res1.open();   res1.close(); } catch(Exception e) {   System.out.println("Exception - 1"); } try (res1 = new Resource()) { //line n1   res1.open(); } catch(Exception e) {   System.out.println("Exception - 2"); } Colored by Color Scripter

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What is the result?
A. Open-Close– Exception – 1 Open–Close–
B. Open–Close–Open–Close–
C. A compilation error occurs at line n1.
D. Open–Close–Open–

Answer: C

Explanation: try-with-resource 구문은 변수선언을 안(line1)에서 해야함.

NEW QUESTION 8
Given the code fragment:

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List<String> words = Arrays.asList("win","try","best","luck","do"); Predicate<String> test1 = w -> {     System.out.println("Checking...");     return w.equals("do");//line n1 }; Predicate test2 = (String w) -> w.length() > 3; //line 2 words.stream().filter(test2).filter(test1).count();   Colored by Color Scripter

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What is the result?
A. A compilation error occurs at line n1.
B. Checking...
C. Checking... Checking...
D. A compilation error occurs at line n2.

Answer: D

Explanation: Predicate<String> 제너릭 타입이 빠져있음

NEW QUESTION 9
Given the code fragment:

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List <String> codes = Arrays.asList("DOC", "MPEG", "JPEG"); codes.forEach(c ->System.out.print(c + " ")); String fmt = codes.stream().filter(s ->s.contains("PEG")).reduce((s, t) ->s + t).get(); System.out.println("\n" + fmt); Colored by Color Scripter

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What is the result?
A. DOC MPEG JPEG
MPEGJPEG
B. DOC MPEG
MPEGJPEG
MPEGMPEGJPEG
C. MPEGJPEG
MPEGJPEG
D. The order of the output is unpredictable.

Answer: A

Explanation: 두번째 라인에서 DOC MPEG JPEG 출력, 네번째라인에서 MPEGJPEG 출력.
reduce() 는 스트림의 요소로 연산한다. 첫번째 요소와 두번째 요소를 비교하여 결과값을 내고, 결과값과 세번째요소, 또 그의 결과값과 네번째요소...연속해서 비교한다.

NEW QUESTION 10
Given the code fragment:

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List < Integer > values = Arrays.asList(1, 2, 3); values.stream().map(n ->n * 2) //line n1 .peek(System.out::print) //line n2 .count(); Colored by Color Scripter

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What is the result?
A. 246
B. The code produces no output.
C. A compilation error occurs at line n1.
D. A compilation error occurs at line n2.

Answer: A

NEW QUESTION 11
Given the code fragment:

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ProductCode < Number, Integer > c1 = new ProductCode < Number, Integer > (); /*c1 instantiantion*/ ProductCode < Number, String > c2 = new ProductCode < Number, String > (); /*c2 instantiation*/  Colored by Color Scripter

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You have been asked to define the ProductCode class. The definition of the ProductCode class must allow c1 instantiation to succeed and cause a compilation error on c2 instantiation.
Which definition of ProductCode meets the requirement?

A. Option A
B. Option B
C. Option C
D. Option D

Answer: B

Explanation: java.lang.Number 부모클래스
● java.lang.Integer 자식클래스

NEW QUESTION 12 Given:

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public class Job {     String name;     Integer cost;     Job(String name, Integer cost){         this.name = name;         this.cost = cost;     }     String getName() { return name; }     int getCost() { return cost; }     public static void main(String[] args){         Job j1 = new Job("IT", null);         DoubleSupplier jS1 = j1::getCost;         System.out.println(j1.getName() + ":" + jS1.getAsDouble());     } } Colored by Color Scripter

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What is the result?

A. IT:null
B. A NullPointerException is thrown at run time.
C. A compilation error occurs.
D. IT:0.0

Answer: B

Explanation: j1::getCost;의 더블콜론은 메소드참조로, 메소드를 호출하는 것이 아니라 메소드 로직 자체를 참조하도록함. Supplier는 매개변수를 받지 않고 특정 타입의 결과를 리턴하는 함수형 인터페이스이다. 결국, 12-13라인은 (double)j1.getCost()을 호출하는 것과 같은데, int타입에는 null이 들어갈수없으므로 jS1.getAsDouble()에서 null포인터exception 난다.

NEW QUESTION 13
Given the code fragment:

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Path p1 = Paths.get("/Pics/MyPic.jpeg"); System.out.println(p1.getNameCount() + ":" + p1.getName(1) + ":" + p1.getFileName());

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Assume that the Pics directory does NOT exist. What is the result?
A. An exception is thrown at run time.
B. 2:MyPic.jpeg: MyPic.jpeg
C. 1:Pics:/Pics/ MyPic.jpeg
D. 2:Pics: MyPic.jpeg

Answer: B

Explanation: getName(int index)- 인덱스 번호에 해당하는 주소를 가진 Path 객체 생성(루트 다음부터 인덱스 0)
, getNameCount()- 루트주소 다음부터 몇 개의 계층으로 이루어져 있는지 갯수 반환


NEW QUESTION 14
Given the code fragment:
Path file = Paths.get ("courses.txt"); // line n1

Assume the courses.txt is accessible.
Which code fragment can be inserted at line n1 to enable the code to print the content of the courses.txt file?

A. List<String> fc = Files.list(file);
fc.stream().forEach (s - > System.out.println(s));
B. Stream<String> fc = Files.readAllLines (file);
fc.forEach (s - > System.out.println(s));
C. List<String> fc = readAllLines(file);
fc.stream().forEach (s - > System.out.println(s));
D. Stream<String> fc = Files.lines (file);
fc.forEach (s - > System.out.println(s));

Answer: D

Explanation:

static List<String>

readAllLines(Path path) Read all lines from a file.

static Stream<String>

lines(Path path) Read all lines from a file as a Stream.

NEW QUESTION 15 Given:

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public final class IceCream {   public void prepare() {} } public class Cake {   public final void bake(int min, int temp) {}   public void mix() {} } public class Shop {   private Cake c = new Cake();   private final double discount = 0.25;   public void makeReady() {     c.bake(10, 120);   } } public class Bread extends Cake {   public void bake(int minutes, int temperature) {}   public void addToppings() {} } Colored by Color Scripter

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Which statement is true?
A. A compilation error occurs in IceCream.
B. A compilation error occurs in Cake.
C. A compilation error occurs in Shop.
D. A compilation error occurs in Bread
E. All classes compile successfully.

Answer: D

Explanation: 클래스에 final이 붙으면 상속시킬수없고, 메소드에 final이 붙으면 오버라이드 할수없다.
16번째라인에서 컴파일 에러 남.

NEW QUESTION 16
Given the code fragment:

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List<String> cs = Arrays.asList("Java","Java EE","Java ME");//line n1 System.out.print(b); Colored by Color Scripter

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Which code fragment, when inserted at line n1, ensures false is printed?
A. boolean b = cs.stream().findAny().get().equals("Java");
B. boolean b = cs.stream().anyMatch(w -> w.equals ("Java"));
C. boolean b = cs.stream().findFirst().get().equals("Java");
D. boolean b = cs.stream().allMatch(w -> w.equals("Java"));

Answer: D

Explanation:
findFirst()와 findAny() 메소드는 해당 스트림에서 첫 번째 요소를 참조하는 Optional 객체를 반환합니다.
anyMatch() : 해당 스트림의 일부 요소가 특정 조건을 만족할 경우에 true를 반환함.
allMatch() : 해당 스트림의 모든 요소가 특정 조건을 만족할 경우에 true를 반환함.

NEW QUESTION 17
Given the code fragment:

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List<String> valList = Arrays.asList("","George","","John","Jim"); Long newVal = valList.stream() // line n1                      .filter(x -> !x.isEmpty())                      .count();    //line n2 System.out.println(newVal); Colored by Color Scripter

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What is the result?
A. A compilation error occurs at line n2.
B. 3
C. 2
D. A compilation error occurs at line n1.

Answer: B

NEW QUESTION 18
Given the content:

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MessageBundle.properties file: inquiry = How are you? MessagesBundle_de_DE.properties file: inquiry = Wie geht's?

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and given the code fragment:

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Locale currentLocale; //line 1 ResourceBundle messages = ResourceBundle.getBundle("MessagesBundle",currentLocale); System.out.println(messages.getString("inquiry")); Colored by Color Scripter

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Which two code fragments, when inserted at line 1 independently, enable the code to print "Wie geht’s?"

A. currentLocale = new Locale("de", "DE");
B. currentLocale = new Locale.Builder().setLanguage("de").setRegion("DE").build();
C. currentLocale = Locale.GERMAN;
D. currentlocale = new Locale();
currentLocale.setLanguage ("de");
currentLocale.setRegion ("DE");
E. currentLocale = Locale.getInstance(Locale.GERMAN,Locale.GERMANY);

Answer: A, B

Explanation:
아래 세 구문이 모두 같은 정의이다.
j4Locale = Locale.JAPAN;
j5Locale = new Locale.Builder().setLanguage("ja").setRegion("JP").build();
j6Locale = new Locale("ja", "JP");

new Locale(); 이러한 생성자는 존재하지 않는다.

Constructor and Description

Locale(String language) Construct a locale from a language code.

Locale(String language, String country) Construct a locale from language and country.

Locale(String language, String country, String variant) Construct a locale from language, country and variant.

NEW QUESTION 19
Given:

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public class Foo<K, V> {     private K key;     private V value;         public Foo(K key, V value){         this.key = key;         this.value = value;     }     public static <T> Foo<T, T> twice(T value){         return new Foo<T, T>(value, value);     }     public K getKey(){ return key; }     public V getValue(){ return value; } } Colored by Color Scripter

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Which option fails?
A. Foo<String, Integer> mark = new Foo<String, Integer> ("Steve", 100);
B. Foo<String, String> pair = Foo.<String>twice ("Hello World!");
C. Foo<Object, Object> percentage = new Foo<String, Integer>("Steve", 100);
D. Foo<String, String> grade = new Foo <> ("John", "A");

Answer: C

Explanation: String, Integer가 Object로 convert될 수없다.

NEW QUESTION 20
Given the code fragment:

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public static void main(String[] args){     Stream.of("Java","Unix","Linux").filter(s-> s.contains("n"))                                     .peek(s -> System.out.println("PEEK: " + s));//line n1 } Colored by Color Scripter

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Which two code fragments, when inserted at line n1 independently, result in the output PEEK: Unix?
A. .anyMatch ();
B. .allMatch ();
C. .findAny ();
D. .noneMatch ();
E. .findFirst ();

Answer: C,E

Explanation:
findFirst()와 findAny() 메소드는 해당 스트림에서 첫 번째 요소를 참조하는 Optional 객체를 반환합니다.
anyMatch() : 해당 스트림의 일부 요소가 특정 조건을 만족할 경우에 true를 반환함.
allMatch() : 해당 스트림의 모든 요소가 특정 조건을 만족할 경우에 true를 반환함.