1Z0-811 Practice Test 15 — 15 Questions

Question 1

Which TWO statements are true about the switch statement in Java? (Choose two.)

Accepted Answer

It can be used with char variables.. Options A and C are correct. A: Switch supports char, int, short, byte, String, and enum types, so char is valid. B is false because the break statement is optional; without it, execution falls through to the next case. C is true: the default case is optional. D is false because case labels must be compile-time constant expressions, not runtime expressions. E is false because long variables are not allowed in switch statements.

Answer

The break statement is mandatory at the end of each case.

Answer

Case labels can be runtime expressions.

Answer

It can be used with long variables.

Question 2

Which TWO statements about interfaces in Java are true?

Accepted Answer

An interface can extend another interface. Interfaces can extend other interfaces and can have default methods with a body.

Answer

An interface can have instance variables

Answer

An interface can implement another interface

Answer

An interface can have final methods

Question 3

Which access modifier allows a member to be accessed only within the same class?

Accepted Answer

private. Private members are accessible only within the same class.

Answer

static

Answer

public

Answer

default (no modifier)

Answer

protected

Question 4

Refer to the exhibit.

What is the output?

Accepted Answer

Photo. The object is Photo, and print() is overridden, so dynamic binding calls Photo's print method.

Answer

Runtime error

Answer

No output

Answer

Compilation error

Answer

Document

Question 5

class Parent { void show() { System.out.print("Parent"); } }
class Child extends Parent { void show() { System.out.print("Child"); } }
public class Test { public static void main(String[] args) { Parent p = new Child(); p.show(); } }

What is the output?

Accepted Answer

Child. Although the reference is Parent, the object is Child, and show() is overridden, so Child's version is called.

Answer

Compilation error

Answer

No output

Answer

Parent

Answer

Runtime error

Question 6

Consider the following interface: public interface Drawable { void draw(); } A developer implements Drawable in class Circle. Which statement about the implementation is correct?

Accepted Answer

The draw method must be declared public. Interface methods are implicitly public and abstract unless declared as default or static. In this interface, draw() is abstract, so it cannot have a body. Therefore, the implementing class must declare draw() as public (making A correct). Option D is false because the interface method has no body. Option C is false because Circle provides an implementation, so the condition for being abstract is not met. Thus, only A is correct, making B incorrect.

Answer

Both A and D

Answer

The class must be abstract if it does not provide body for draw

Answer

The draw method can have a body in the interface

Answer

The draw method must be declared final

Question 7

Refer to the exhibit. Why does the code fail to compile?

Accepted Answer

Cannot instantiate an abstract class. Abstract classes cannot be instantiated. The attempt to create a new Animal() causes a compile-time error because Animal is abstract.

Answer

Animal must be declared as interface

Answer

The main method is in the wrong class

Answer

The sound() method is not defined

Question 8

Which TWO of the following are valid ways to create a String?

Accepted Answer

String s = new String("Hello");. It uses the `new` keyword to explicitly create a new String object in the heap, which is a valid way to instantiate a String. Option E is correct because it uses a string literal, which is the most common and efficient way to create a String in Java, leveraging the string constant pool.

Answer

String s = 'Hello';

Answer

String s = 123;

Answer

String s = String.valueOf("Hello");

Question 9

Given boolean a = true, b = false, c = true; What is the result of (a || b) && (b || c)?

Accepted Answer

true. a||b = true, b||c = true, true && true = true.

Answer

Short-circuit evaluation prevents evaluation

Answer

Compilation error

Answer

false

Question 10

Which TWO statements are true about the String class in Java? (Choose 2)

Accepted Answer

Strings are immutable.. The correct answers are C and E. Option C is true because String objects in Java are immutable; once created, they cannot be changed. Option E is true because the intern() method places the string into the string pool if it is not already present, allowing reuse of string literals. Option A is false: String is immutable regardless of whether it is created with new or a literal. Option B is false: String does not implement Cloneable; it implements Serializable, Comparable, and CharSequence. Option D is false: methods like toUpperCase() return a new String object and do not modify the original.

Answer

String is mutable if created with new.

Answer

String implements the Cloneable interface.

Answer

String objects can be modified using methods like toUpperCase().

Question 11

Given: int x = 10; int y = 20; What is the output of System.out.println(x + y * 2);?

Accepted Answer

50. Multiplication has higher precedence than addition: y * 2 = 40, then x + 40 = 50.

Answer

40

Answer

60

Answer

30

Question 12

What is the output of the following code? String s1 = "Hello"; String s2 = "Hello"; System.out.println(s1 == s2);

Accepted Answer

true. String literals are interned, so both references point to the same object in the string pool, and == compares references, resulting in true.

Answer

Hello

Answer

Compilation error

Answer

false

Question 13

Which TWO of the following are valid declarations and initializations of primitive variables?

Accepted Answer

double d = 10.5;. Options A and C are correct. A: double d = 10.5; is valid because a double literal can be assigned without suffix. C: int i = 10; is valid because 10 fits in an int. B: float f = 10.5; is invalid because 10.5 is a double literal; must use f suffix. D: byte b = 200; is invalid because 200 is out of byte range (-128 to 127). E: long l = 123456789012; is invalid because the literal exceeds int range and lacks L suffix.

Answer

float f = 10.5;

Answer

byte b = 200;

Answer

long l = 123456789012;

Question 14

What is the value of the expression: 2 + 3 * 4 / 2 - 1?

Accepted Answer

7. Operator precedence: multiplication and division have higher precedence than addition/subtraction, and they are evaluated left-to-right. So 3*4=12, 12/2=6, 2+6=8, 8-1=7.

Answer

9

Answer

10

Answer

3

Question 15

Given: String s1 = "Java"; String s2 = new String("Java"); What does (s1 == s2) evaluate to?

Accepted Answer

false. S1 is a string literal which is interned, while s2 is created using the 'new' keyword, resulting in a different object in heap memory. The '==' operator compares object references, so it returns false. Option A is incorrect because 'true if interned' is misleading; s1 is interned, but the comparison is false because s2 is a separate object. Option C ('true') is wrong because references differ. Option D ('Compilation error') is incorrect; the code compiles and runs without error.

Answer

true if interned, false otherwise

Answer

true

Answer

Compilation error