Pass the Oracle Java SE 1z0-830 Questions and answers with ExamsMirror

In this code, the strip() method is used to remove leading and trailing whitespace from strings. The strip() method, introduced in Java 11, is Unicode-aware and removes all leading and trailing characters that are considered whitespace according to the Unicode standard.

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Analysis of Each Statement:

First Statement:

java

String s = " ";

System.out.print("[" + s.strip());

The string s contains four spaces.

Applying s.strip() removes all leading and trailing spaces, resulting in an empty string.

The output is "[" followed by the empty string, so the printed result is "[".

Second Statement:

java

s = " hello ";

System.out.print("," + s.strip());

The string s is now " hello ".

Applying s.strip() removes all leading and trailing spaces, resulting in "hello".

The output is "," followed by "hello", so the printed result is ",hello".

Third Statement:

java

s = "h i ";

System.out.print("," + s.strip() + "]");

The string s is now "h i ".

Applying s.strip() removes the trailing spaces, resulting in "h i".

The output is "," followed by "h i" and then "]", so the printed result is ",h i]".

Combined Output:

Combining all parts, the final output is:

css

[,hello,h i]

In the provided code, we have two inner classes within the Test class:

Class A:

An inner (non-static) class.

Instances of A are associated with an instance of the enclosing Test class.

Class B:

A static nested class.

Instances of B are not associated with any instance of the enclosing Test class and can be instantiated without an instance of Test.

Evaluation of Statements:

A. A a = new A();

Invalid.Since A is a non-static inner class, it requires an instance of the enclosing class Test to be instantiated. Attempting to instantiate A without an instance of Test will result in a compilation error.

B. B b = new Test.B();

Valid.B is a static nested class and can be instantiated without an instance of Test. This syntax is correct.

C. A a = new Test.A();

Invalid.Even though A is referenced through Test, it is a non-static inner class and requires an instance of Test for instantiation. This will result in a compilation error.

D. B b = new Test().new B();

Invalid.While this syntax is used for instantiating non-static inner classes, B is a static nested class and does not require an instance of Test. This will result in a compilation error.

E. B b = new B();

Valid.Since B is a static nested class, it can be instantiated directly without referencing the enclosing class.

F. A a = new Test().new A();

Valid.This is the correct syntax for instantiating a non-static inner class. An instance of Test is created, and then an instance of A is created associated with that Test instance.

Therefore, the valid statements are B, E, and F.

Understanding TreeMap.subMap(fromKey, fromInclusive, toKey, toInclusive)

TreeMap.subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) returns aportion of the mapthat falls within the specified key range.

Thefirst boolean parameter(fromInclusive) determines if the fromKey should be included.

Thesecond boolean parameter(toInclusive) determines if the toKey should be included.

Given TreeMap Contents

CopyEdit

{1=Moulin Rouge, 2=Crazy Horse, 3=Paradis Latin, 4=Le Lido, 5=Folies Bergère}

Applying subMap(2, true, 5, false)

Includeskey 2 ("Crazy Horse")✅(fromInclusive = true)

Includeskey 3 ("Paradis Latin")✅

Includeskey 4 ("Le Lido")✅

Excludes key 5 ("Folies Bergère")❌(toInclusive = false)

Final Output

CopyEdit

{2=Crazy Horse, 3=Paradis Latin, 4=Le Lido}

Thus, the correct answer is:✅{2=Crazy Horse, 3=Paradis Latin, 4=Le Lido}

References:

Java SE 21 - TreeMap.subMap()

Java SE 21 - NavigableMap

In this code, the SmartPhone interface declares a method ring() with a boolean return type. The Iphone15 class implements the SmartPhone interface and provides an implementation for the ring() method.

However, in the Iphone15 class, the ring() method is declared without the public access modifier. In Java, when a class implements an interface, it must provide implementations for all the interface's methods with the same or a more accessible access level. Since interface methods are implicitly public, the implementing methods in the class must also be public. Failing to do so results in a compilation error.

Therefore, the Iphone15 class does not compile because the ring() method is not declared as public.

In Java, records are a special kind of class designed to act as transparent carriers for immutabledata. They automatically provide implementations for equals(), hashCode(), and toString(), and their fields are final and private by default.

Option A: ExtendingClass

Analysis: Records in Java implicitly extend java.lang.Record and cannot extend any other class because Java does not support multiple inheritance. Attempting to extend another class, such as Exception, will result in a compilation error.

Conclusion: Does not compile.

Option B: WithInstanceField

Analysis: Records do not allow the declaration of instance fields outside of their components. The declaration of double fuz; is not permitted and will cause a compilation error.

Conclusion: Does not compile.

Option C: ImplementingInterface

Analysis: Records can implement interfaces. In this case, ImplementingInterface implements Cloneable, which is valid.

Conclusion: Compiles successfully.

To achieve the output "August 08", the SimpleDateFormat pattern must format the month in its full textual form and the day as a two-digit number.

Pattern Analysis:

MMMM: Represents the full name of the month (e.g., "August").

dd: Represents the day of the month as a two-digit number, with leading zeros if necessary (e.g., "08").

Therefore, the correct pattern to produce the desired output is MMMM dd.

Option Evaluations:

A. MM d: Formats the month as a two-digit number and the day as a single or two-digit number without leading zeros. For example, "08 8".

B. MM dd: Formats the month and day both as two-digit numbers. For example, "08 08".

C. MMMM dd: Formats the month as its full name and the day as a two-digit number. For example, "August 08".

D. MMM dd: Formats the month as its abbreviated name and the day as a two-digit number. For example, "Aug 08".

Thus, option C (MMMM dd) is the correct choice to match the output "August 08".

Understanding do-while Execution

A do-while loopexecutes at least oncebefore checking the condition.

++counter < 3 increments counterbeforeevaluating the condition.

Step-by-Step Execution

Iteration 1:counter = 0, print "0", then ++counter becomes 1, condition 1 < 3 istrue.

Iteration 2:counter = 1, print "1", then ++counter becomes 2, condition 2 < 3 istrue.

Iteration 3:counter = 2, print "2", then ++counter becomes 3, condition 3 < 3 isfalse, so loop exits.

Final Output

0 1 2

Thus, the correct answer is:0 1 2

References:

Java SE 21 - Control Flow Statements

Java SE 21 - do-while Loop

Error in for Loop Initialization

The initialization part of a for loopcannot declare multiple variables with different types in a single statement.

Error:

java

for (int i = 0, int j = 3; i < j; i++) {

Fix:Declare variables separately:

java

for (int i = 0, j = 3; i < j; i++) {

lyrics.lines() in Java 21

The lines() method of String returns aStream<String>, splitting the string by line breaks.

Calling .toList() on a streamconverts it to a list.

Valid Code After Fixing the Loop:

java

var lyrics = """

Quand il me prend dans ses bras

Qu'il me parle tout bas

Je vois la vie en rose

""";

for (int i = 0, j = 3; i < j; i++) {

System.out.println(lyrics.lines()

toList()

get(i));

}

Expected Output After Fixing:

vbnet

Quand il me prend dans ses bras

Qu'il me parle tout bas

Je vois la vie en rose

Thus, the correct answer is:Compilation fails.

References:

Java SE 21 - String.lines()

Java SE 21 - for Statement Rules

Understanding Sealed Classes in Java

Asealed classrestricts which other classes can extend it.

A sealed classmust explicitly declare its permitted subclassesusing the permits keyword.

Subclasses can be declared as:

sealed(restricts further extension).

non-sealed(removes the restriction, allowing unrestricted subclassing).

final(prevents further subclassing).

Analyzing the Given Code

Vehicle is declared as sealed with permits Car, Bike, meaning only Car and Bike can extend it.

Car is declared as non-sealed, which means itis no longer sealedand can have subclasses.

Bike is declared as final, meaningit cannot be subclassed.

Using isSealed() Method

vehicleClass.isSealed() →truebecause Vehicle is explicitly marked as sealed.

carClass.isSealed() →falsebecause Car is marked non-sealed.

bikeClass.isSealed() →falsebecause Bike is final, and a final class isnot considered sealed.

Final Output

csharp

Is Vehicle sealed? true; Is Car sealed? false; Is Bike sealed? false

Thus, the correct answer is:"Is Vehicle sealed? true; Is Car sealed? false; Is Bike sealed? false"

References:

Java SE 21 - Sealed Classes

Java SE 21 - isSealed() Method

In this code, a text block is defined using the """ syntax introduced in Java 13. Text blocks allow for multiline string literals, preserving the format as written in the code.

Text Block Analysis:

The text block is defined as:

java

String textBlock = """

j \

a \t

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