1Z0-811 Primitives, Strings and Operators Practice Test 5 — 15 Questions

Question 1

Which of the following is NOT a primitive data type?

Accepted Answer

String. String is a class in Java, not a primitive data type. The eight primitive types are byte, short, int, long, float, double, boolean, and char. String is a reference type that stores a sequence of characters as an object.

Answer

int

Answer

boolean

Answer

char

Question 2

What is the output of the following code? int i = 0; i = i++ + ++i; System.out.println(i);

Accepted Answer

2. The expression `i = i++ + ++i` evaluates as follows: initially `i = 0`. In `i++`, the post-increment operator returns the current value (0) and then increments `i` to 1. Then `++i` pre-increments `i` from 1 to 2 and returns 2. The sum is 0 + 2 = 2, which is assigned to `i`, overwriting the intermediate increments. Thus, the final output is 2.

Answer

3

Answer

0

Answer

1

Question 3

Which of the following is a valid declaration of a float variable?

Accepted Answer

Both B and D are valid. Options B and D are valid because they use the f or F suffix to explicitly denote a float literal. Option C is invalid because 10.5 is a double literal and cannot be implicitly converted to float without a cast or suffix.

Answer

float f = 10.5f;

Answer

float f = 10.5;

Answer

float f = 10.5F;

Question 4

What is the value of 10 % 3?

Accepted Answer

1. The % operator returns remainder of division. 10 divided by 3 is 3 with remainder 1.

Answer

0

Answer

1.0

Answer

3

Question 5

Which keyword is used to declare a constant in Java?

Accepted Answer

final. The final keyword declares a variable whose value cannot be changed. const and constant are not used.

Answer

constant

Answer

static

Answer

const

Question 6

What is the result of the following code? Integer a = 100; Integer b = 100; System.out.println(a == b);

Accepted Answer

true. Java caches Integer objects for values between -128 and 127. When autoboxing converts the int literal 100 to an Integer object, both a and b reference the same cached object. Therefore, the == operator, which compares object references, returns true.

Answer

false

Answer

Compilation error

Answer

Runtime exception

Question 7

What is the output of the following code?
String str1 = "Java";
String str2 = new String("Java");
System.out.println(str1 == str2);

Accepted Answer

false. The == operator compares object references. One string is a literal (stored in the string pool) and the other is created using the 'new' keyword (heap object). They are different references, so the comparison returns false.

Answer

true

Answer

Compilation error

Answer

Java

Question 8

Refer to the exhibit. What is the result?

Accepted Answer

Runtime exception. The code attempts to divide an integer by zero, which in Java throws an ArithmeticException at runtime. Since the division is performed with integer operands (int / int), Java does not allow division by zero and raises an exception, not a floating-point infinity or zero. Therefore, the correct answer is C: Runtime exception.

Answer

Compilation error

Answer

0

Answer

Infinity

Question 9

Refer to the exhibit. What is the output?

Accepted Answer

true. The code uses `==` to compare two `String` objects created with string literals (e.g., `String s1 = "true"; String s2 = "true";`). In Java, string literals are interned, meaning they refer to the same object in the string pool. Therefore, the reference comparison returns `true`. The `==` operator checks reference equality, not content equality, but due to interning, the references are the same. If `new String("true")` were used, the comparison would be `false` because different objects are created.

Answer

Runtime exception

Answer

Compilation error

Answer

false

Question 10

Which two of the following are primitive data types in Java? (Choose two)

Accepted Answer

boolean. `boolean` is a primitive data type in Java that can hold only two values: `true` or `false`. It is not an object and does not have methods, making it a fundamental building block for conditional logic.

Answer

Character

Answer

String

Answer

Integer

Question 11

Which two expressions evaluate to true? (Choose two)

Accepted Answer

10 > 5. The expression `10 > 5` uses the greater-than operator, which evaluates to `true` since 10 is indeed greater than 5. Option D is correct because `!false` evaluates to `true`, and the logical OR operator (`||`) returns `true` if at least one operand is `true`, so `false || true` yields `true`.

Answer

true && false

Answer

'a' == 'b'

Answer

3 < 3

Question 12

Which three statements about String immutability are true? (Choose three)

Accepted Answer

The intern() method returns a String from the pool. The `intern()` method returns a canonical representation of the string from the string pool, ensuring that strings with the same content share the same memory reference, which is a key aspect of immutability and memory optimization in Java.

Answer

String objects can be modified after creation

Answer

String objects can be changed by calling methods

Question 13

What is the result of the following code snippet? int x = 5; int y = 2; double z = x / y; System.out.println(z);

Accepted Answer

2.0. In Java, when both operands of the division operator are integers (int), the operation performs integer division, which truncates the fractional part. Here, x / y = 5 / 2 = 2 (integer division), and then the result is implicitly widened to double when assigned to z, producing 2.0.

Answer

3.0

Answer

2

Answer

2.5

Question 14

Which of the following is a valid Java primitive type?

Accepted Answer

boolean. `boolean` is one of the eight primitive data types defined in the Java Language Specification (JLS §4.2). It represents a single bit of information with only two possible values: `true` or `false`, and is not an object or a reference type.

Answer

String

Answer

Integer

Answer

Char

Question 15

A developer needs to concatenate several string values in a loop. Which approach is most efficient for performance?

Accepted Answer

Using StringBuilder. StringBuilder is the most efficient approach for concatenating strings in a loop because it maintains a mutable sequence of characters, avoiding the creation of intermediate String objects. In contrast, using the '+' operator or String.concat() inside a loop results in the allocation of a new String object for each concatenation, leading to O(n²) time complexity and increased garbage collection overhead.

Answer

Using String.concat()

Answer

Using the '+' operator inside the loop

Answer

Using StringBuffer