1z1-830試験無料問題集（85題）「Oracle Java SE 21 Developer Professional 認定」

出題：1

Given:
java
Object myVar = 0;
String print = switch (myVar) {
case int i -> "integer";
case long l -> "long";
case String s -> "string";
default -> "";
};
System.out.println(print);
What is printed?

A. Compilation fails.

B. string

C. long

D. integer

E. nothing

F. It throws an exception at runtime.

正解：A 解答を投票する

解説: (GoShiken メンバーにのみ表示されます)

出題：2

Which of the followingisn'ta correct way to write a string to a file?

A. java
try (FileOutputStream outputStream = new FileOutputStream("file.txt")) { byte[] strBytes = "Hello".getBytes(); outputStream.write(strBytes);
}

B. java
try (BufferedWriter writer = new BufferedWriter("file.txt")) {
writer.write("Hello");
}

C. None of the suggestions

D. java
Path path = Paths.get("file.txt");
byte[] strBytes = "Hello".getBytes();
Files.write(path, strBytes);

E. java
try (PrintWriter printWriter = new PrintWriter("file.txt")) {
printWriter.printf("Hello %s", "James");
}

F. java
try (FileWriter writer = new FileWriter("file.txt")) {
writer.write("Hello");
}

正解：B 解答を投票する

解説: (GoShiken メンバーにのみ表示されます)

出題：3

Given:
java
var sList = new CopyOnWriteArrayList<Customer>();
Which of the following statements is correct?

A. Element-changing operations on iterators of CopyOnWriteArrayList, such as remove, set, and add, are supported and do not throw UnsupportedOperationException.

B. The CopyOnWriteArrayList class is not thread-safe and does not prevent interference amongconcurrent threads.

C. The CopyOnWriteArrayList class's iterator reflects all additions, removals, or changes to the list since the iterator was created.

D. The CopyOnWriteArrayList class is a thread-safe variant of ArrayList where all mutative operations are implemented by making a fresh copy of the underlying array.

E. The CopyOnWriteArrayList class does not allow null elements.

正解：D 解答を投票する

解説: (GoShiken メンバーにのみ表示されます)

出題：4

Given:
java
String s = " ";
System.out.print("[" + s.strip());
s = " hello ";
System.out.print("," + s.strip());
s = "h i ";
System.out.print("," + s.strip() + "]");
What is printed?

A. [ ,hello,h i]

B. [ , hello ,hi ]

C. [,hello,h i]

D. [,hello,hi]

正解：C 解答を投票する

解説: (GoShiken メンバーにのみ表示されます)

出題：5

Given:
java
final Stream<String> strings =
Files.readAllLines(Paths.get("orders.csv"));
strings.skip(1)
.limit(2)
.forEach(System.out::println);
And that the orders.csv file contains:
mathematica
OrderID,Customer,Product,Quantity,Price
1,Kylian Mbappe,Keyboard,2,25.50
2,Teddy Riner,Mouse,1,15.99
3,Sebastien Loeb,Monitor,1,199.99
4,Antoine Griezmann,Headset,3,45.00
What is printed?

A. arduino
1,Kylian Mbappe,Keyboard,2,25.50
2,Teddy Riner,Mouse,1,15.99
3,Sebastien Loeb,Monitor,1,199.99
4,Antoine Griezmann,Headset,3,45.00

B. arduino
2,Teddy Riner,Mouse,1,15.99
3,Sebastien Loeb,Monitor,1,199.99

C. Compilation fails.

D. An exception is thrown at runtime.

E. arduino
1,Kylian Mbappe,Keyboard,2,25.50
2,Teddy Riner,Mouse,1,15.99

正解：C,D 解答を投票する

解説: (GoShiken メンバーにのみ表示されます)

出題：6

Given:
java
CopyOnWriteArrayList<String> list = new CopyOnWriteArrayList<>();
list.add("A");
list.add("B");
list.add("C");
// Writing in one thread
new Thread(() -> {
list.add("D");
System.out.println("Element added: D");
}).start();
// Reading in another thread
new Thread(() -> {
for (String element : list) {
System.out.println("Read element: " + element);
}
}).start();
What is printed?

A. It prints all elements, including changes made during iteration.

B. It prints all elements, but changes made during iteration may not be visible.

C. Compilation fails.

D. It throws an exception.

正解：B 解答を投票する

解説: (GoShiken メンバーにのみ表示されます)

出題：7

Given:
java
public class OuterClass {
String outerField = "Outer field";
class InnerClass {
void accessMembers() {
System.out.println(outerField);
}
}
public static void main(String[] args) {
System.out.println("Inner class:");
System.out.println("------------");
OuterClass outerObject = new OuterClass();
InnerClass innerObject = new InnerClass(); // n1
innerObject.accessMembers(); // n2
}
}
What is printed?

A. Nothing

B. An exception is thrown at runtime.

C. Compilation fails at line n2.

D. Compilation fails at line n1.

E. markdown
Inner class:
------------
Outer field

正解：D 解答を投票する

解説: (GoShiken メンバーにのみ表示されます)

出題：8

Given:
java
var ceo = new HashMap<>();
ceo.put("Sundar Pichai", "Google");
ceo.put("Tim Cook", "Apple");
ceo.put("Mark Zuckerberg", "Meta");
ceo.put("Andy Jassy", "Amazon");
Does the code compile?

A. True

B. False

正解：B 解答を投票する

解説: (GoShiken メンバーにのみ表示されます)

1z1-830試験無料問題集「Oracle Java SE 21 Developer Professional 認定」