Oracle 1z0-830 Exam With Confidence Using Practice Dumps

In this code, a Stream of String elements is created containing the characters "J", "a", "v", and "a". The reduce method is then used with String::concat as the accumulator function.

The reduce method with a single BinaryOperator parameter performs a reduction on the elements of the stream, using an associative accumulation function, and returns an Optional describing the reduced value, if any. In this case, it concatenates the strings in the stream.

Since the stream contains elements, the reduction operation concatenates them to form the string "Java". The result is wrapped in an Optional, resulting in Optional[Java]. The print statement outputs this Optional object, displaying Optional[Java].

In this code, a Stream of String elements is created containing "United" and "States". A BinaryOperator named operator is defined to concatenate the first string (s1) with the uppercase version of the second string (s2). The reduce method is then used with "-" as the identity value and operator as the accumulator.

The reduce method processes the elements of the stream as follows:

Initial Identity Value: "-"

First Iteration:

Accumulator Operation: "-".concat("United".toUpperCase())

Result: "-UNITED"

Second Iteration:

Accumulator Operation: "-UNITED".concat("States".toUpperCase())

Result: "-UNITEDSTATES"

Therefore, the final result stored in result is "-UNITEDSTATES", and the output of theSystem.out.println(result); statement is -UNITEDSTATES.

Understanding ExecutorService Methods

execute(Runnable command)

Runs the task but only supports Runnable (not Callable).

❌execService.execute(task2); fails because task2 is Callable.

submit(Runnable task)

Submits a Runnable task for execution.

execService.submit(task1); executes "Executing Task-1".

submit(Callable<T> task)

Submits a Callable task for execution.

execService.submit(task2); executes "Executing Task-2".

call() Does Not Exist in ExecutorService

❌execService.call(task1); and execService.call(task2); are invalid.

run() Does Not Exist in ExecutorService

❌execService.run(task1); and execService.run(task2); are invalid.

Correct Code to Print Both Messages:

java

execService.submit(task1);

execService.submit(task2);

Thus, the correct answer is:execService.submit(task1); execService.submit(task2);

References:

Java SE 21 - ExecutorService

Java SE 21 - Callable and Runnable