1z0-830無料問題集「Oracle Java SE 21 Developer Professional」

質問 1

Given:
java
var array1 = new String[]{ "foo", "bar", "buz" };
var array2[] = { "foo", "bar", "buz" };
var array3 = new String[3] { "foo", "bar", "buz" };
var array4 = { "foo", "bar", "buz" };
String array5[] = new String[]{ "foo", "bar", "buz" };
Which arrays compile? (Select 2)

（A）array2

（B）array4

（C）array3

（D）array1

（E）array5

正解：D、E 解答を投票する

解説: (JPNTest メンバーにのみ表示されます)

質問 2

What do the following print?
java
public class DefaultAndStaticMethods {
public static void main(String[] args) {
WithStaticMethod.print();
}
}
interface WithDefaultMethod {
default void print() {
System.out.print("default");
}
}
interface WithStaticMethod extends WithDefaultMethod {
static void print() {
System.out.print("static");
}
}

（A）Compilation fails

（B）static

（C）nothing

（D）default

正解：B 解答を投票する

解説: (JPNTest メンバーにのみ表示されます)

質問 3

How would you create a ConcurrentHashMap configured to allow a maximum of 10 concurrent writer threads and an initial capacity of 42?
Which of the following options meets this requirement?

（A）var concurrentHashMap = new ConcurrentHashMap(42, 10);

（B）var concurrentHashMap = new ConcurrentHashMap(42);

（C）var concurrentHashMap = new ConcurrentHashMap(42, 0.88f, 10);

（D）var concurrentHashMap = new ConcurrentHashMap();

（E）None of the suggestions.

正解：C 解答を投票する

解説: (JPNTest メンバーにのみ表示されます)

質問 4

Given:
java
interface SmartPhone {
boolean ring();
}
class Iphone15 implements SmartPhone {
boolean isRinging;
boolean ring() {
isRinging = !isRinging;
return isRinging;
}
}
Choose the right statement.

（A）SmartPhone interface does not compile

（B）Everything compiles

（C）An exception is thrown at running Iphone15.ring();

（D）Iphone15 class does not compile

正解：D 解答を投票する

解説: (JPNTest メンバーにのみ表示されます)

質問 5

Given:
java
void verifyNotNull(Object input) {
boolean enabled = false;
assert enabled = true;
assert enabled;
System.out.println(input.toString());
assert input != null;
}
When does the given method throw a NullPointerException?

（A）Only if assertions are enabled and the input argument is null

（B）A NullPointerException is never thrown

（C）Only if assertions are disabled and the input argument is null

（D）Only if assertions are disabled and the input argument isn't null

（E）Only if assertions are enabled and the input argument isn't null

正解：C 解答を投票する

解説: (JPNTest メンバーにのみ表示されます)

質問 6

Given:
java
interface A {
default void ma() {
}
}
interface B extends A {
static void mb() {
}
}
interface C extends B {
void ma();
void mc();
}
interface D extends C {
void md();
}
interface E extends D {
default void ma() {
}
default void mb() {
}
default void mc() {
}
}
Which interface can be the target of a lambda expression?

（A）E

（B）D

（C）B

（D）None of the above

（E）C

（F）A

正解：D 解答を投票する

解説: (JPNTest メンバーにのみ表示されます)

質問 7

Given:
java
System.out.print(Boolean.logicalAnd(1 == 1, 2 < 1));
System.out.print(Boolean.logicalOr(1 == 1, 2 < 1));
System.out.print(Boolean.logicalXor(1 == 1, 2 < 1));
What is printed?

（A）truetruetrue

（B）truetruefalse

（C）Compilation fails

（D）truefalsetrue

（E）falsetruetrue

正解：D 解答を投票する

解説: (JPNTest メンバーにのみ表示されます)

質問 8

You are working on a module named perfumery.shop that depends on another module named perfumery.
provider.
The perfumery.shop module should also make its package perfumery.shop.eaudeparfum available to other modules.
Which of the following is the correct file to declare the perfumery.shop module?

（A）File name: module.java
java
module shop.perfumery {
requires perfumery.provider;
exports perfumery.shop.eaudeparfum;
}

（B）File name: module-info.perfumery.shop.java
java
module perfumery.shop {
requires perfumery.provider;
exports perfumery.shop.eaudeparfum.*;
}

（C）File name: module-info.java
java
module perfumery.shop {
requires perfumery.provider;
exports perfumery.shop.eaudeparfum;
}

正解：C 解答を投票する

解説: (JPNTest メンバーにのみ表示されます)

質問 9

Given:
java
var _ = 3;
var $ = 7;
System.out.println(_ + $);
What is printed?

（A）10

（B）_$

（C）It throws an exception.

（D）Compilation fails.

正解：D 解答を投票する

解説: (JPNTest メンバーにのみ表示されます)

1z0-830 無料問題集「Oracle Java SE 21 Developer Professional」

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