Oracle Updated 1z0-830 Exam Questions and Answers by gia

In this code, a Stream containing the elements "a" and "b" is processed using the collect method. The collect method is a terminal operation that performs a mutable reduction on the elements of the stream using a Collector. In this case, custom implementations for the supplier, accumulator, and combiner are provided.

Components of the collect Method:

Supplier:

() -> new StringBuilder("c")

This supplier creates a new StringBuilder initialized with the string "c".

Accumulator:

StringBuilder::append

This accumulator appends each element of the stream to the StringBuilder.

Combiner:

(a, b) -> b.append(a)

This combiner is used in parallel stream operations to merge two StringBuilder instances. It appends the contents of a to b.

Execution Flow:

Stream Elements:"a", "b"

Initial StringBuilder:"c"

Accumulation:

The first element "a" is appended to "c", resulting in "ca".

The second element "b" is appended to "ca", resulting in "cab".

Combiner:

In this sequential stream, the combiner is not utilized. The combiner is primarily used in parallel streams to merge partial results.

Final Result:

The StringBuilder contains "cab". Therefore, the output of the program is:

nginx

cab

In this code, a double variable amount is initialized to 42,000.00. The NumberFormat.getCompactNumberInstance(Locale.FRANCE, NumberFormat.Style.SHORT) method is used to obtain a compact number formatter for the French locale with the short style. The format method is then called to format the amount.

The compact number formatting is designed to represent numbers in a shorter form, based on the patterns provided for a given locale. In the French locale, the short style represents thousands with a lowercase 'k'. Therefore, 42,000 is formatted as 42 k.

Option Evaluations:

A. 42000E: This format is not standard in the French locale for compact number formatting.

B. 42 000,00 €: This represents the number as a currency with two decimal places, which is not the compact form.

C. 42000: This is the plain number without any formatting, which does not match the compact number format.

D. 42 k: This is the correct compact representation of 42,000 in the French locale with the short style.

Thus, option D (42 k) is the correct output.

Understanding Multi-line Strings in Java (""" Text Blocks)

Java 13 introducedtext blocks ("""), allowing multi-line stringswithout needing explicit \n for new lines.

In a text block,each line is preserved as it appears in the source code.

Analyzing the Options

Option A: \ (Backslash Continuation)

The backslash (\) at the end of a lineprevents a new line from being added, meaning:

nginx

red green blue

Incorrect.

Option B: \s (Whitespace Escape)

\s represents asingle space,not a new line.

The output would be:

nginx

red green blue

Incorrect.

Option C: \t (Tab Escape)

\t inserts atab, not a new line.

The output would be:

nginx

red green blue

Incorrect.

Option D: Correct Text Block

java

String colors = """

red

green

blue

""";

Thispreserves the new lines, producing:

nginx

red

green

blue

Correct.

Thus, the correct answer is:"String colors = """ red green blue """."

References:

Java SE 21 - Text Blocks

Java SE 21 - String Formatting

Understanding Variable Assignments

java

Integer frenchRevolution = 1789;

Object o1 = new String("1789");

Object o2 = frenchRevolution;

frenchRevolution = null;

frenchRevolution is an Integer with value1789.

o1 is aString with value "1789".

o2 storesa reference to frenchRevolution, which is an Integer (1789).

frenchRevolution = null;only nullifies the reference, but o2 still holds the Integer 1789.

Calling toString() on o2

java

Object o3 = o2.toString();

o2 refers to an Integer (1789).

Integer.toString() returns theString representation "1789".

o3 is assigned "1789" (String).

Evaluating o1.equals(o3)

java

System.out.println(o1.equals(o3));

o1.equals(o3) isequivalent to:

java

"1789".equals("1789")

Since both areequal strings, the output is:

arduino

true

Thus, the correct answer is:true

References:

Java SE 21 - Integer.toString()

Java SE 21 - String.equals()