Free Oracle 1z0-830 Exam Dumps Questions & Answers

Given:
java
StringBuffer us = new StringBuffer("US");
StringBuffer uk = new StringBuffer("UK");
Stream<StringBuffer> stream = Stream.of(us, uk);
String output = stream.collect(Collectors.joining("-", "=", ""));
System.out.println(output);
What is the given code fragment's output?

• A.  -US=UK
• B.  US-UK
• C.  Compilation fails.
• D.  =US-UK
• E.  An exception is thrown.
• F.  US=UK

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

• A.  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.
• B.  The CopyOnWriteArrayList class's iterator reflects all additions, removals, or changes to the list since the iterator was created.
• C.  Element-changing operations on iterators of CopyOnWriteArrayList, such as remove, set, and add, are supported and do not throw UnsupportedOperationException.
• D.  The CopyOnWriteArrayList class does not allow null elements.
• E.  The CopyOnWriteArrayList class is not thread-safe and does not prevent interference amongconcurrent threads.

Which StringBuilder variable fails to compile?
java
public class StringBuilderInstantiations {
public static void main(String[] args) {
var stringBuilder1 = new StringBuilder();
var stringBuilder2 = new StringBuilder(10);
var stringBuilder3 = new StringBuilder("Java");
var stringBuilder4 = new StringBuilder(new char[]{'J', 'a', 'v', 'a'});
}
}

• A.  stringBuilder2
• B.  stringBuilder4
• C.  stringBuilder3
• D.  stringBuilder1
• E.  None of them

Given:
java
try (FileOutputStream fos = new FileOutputStream("t.tmp");
ObjectOutputStream oos = new ObjectOutputStream(fos)) {
fos.write("Today");
fos.writeObject("Today");
oos.write("Today");
oos.writeObject("Today");
} catch (Exception ex) {
// handle exception
}
Which statement compiles?

• A.  oos.writeObject("Today");
• B.  fos.writeObject("Today");
• C.  fos.write("Today");
• D.  oos.write("Today");

Given:
java
DoubleSummaryStatistics stats1 = new DoubleSummaryStatistics();
stats1.accept(4.5);
stats1.accept(6.0);
DoubleSummaryStatistics stats2 = new DoubleSummaryStatistics();
stats2.accept(3.0);
stats2.accept(8.5);
stats1.combine(stats2);
System.out.println("Sum: " + stats1.getSum() + ", Max: " + stats1.getMax() + ", Avg: " + stats1.getAverage()); What is printed?

• A.  Compilation fails.
• B.  Sum: 22.0, Max: 8.5, Avg: 5.0
• C.  Sum: 22.0, Max: 8.5, Avg: 5.5
• D.  An exception is thrown at runtime.