1Z0-811 Java Basics and Syntax Practice Test 3 — 15 Questions

Question 1

A class defines a static variable initialized at declaration: static int count = 10;. A static method attempts to modify it: count = 20;. Which statement is true?

Accepted Answer

The variable can be changed to 20. Static variables belong to the class, not instances, and can be accessed and modified by static methods. The assignment `count = 20;` is valid and changes the value from 10 to 20 at runtime.

Answer

The variable cannot be accessed from a static method

Answer

The code causes a compilation error

Answer

The variable is read-only

Question 2

A developer uses a switch statement with a String variable. Which is true about this usage?

Accepted Answer

It works with strings starting from Java 7. Starting from Java 7 (JSR 334), the switch statement supports String objects in addition to primitive types and enums. The compiler uses the `hashCode()` and `equals()` methods of the String class to evaluate the switch expression against case labels, making it a valid and efficient way to branch on string values.

Answer

It works only with primitive types

Answer

It causes a compilation error because strings are not supported

Answer

It requires a default case

Question 3

Which loop construct guarantees that the loop body executes at least once?

Accepted Answer

do-while loop. The do-while loop is the only Java loop construct that guarantees the loop body executes at least once because the condition is evaluated after the body executes. In contrast, the while and for loops evaluate the condition before the first iteration, so the body may never execute if the condition is initially false. The enhanced for loop also checks for elements before entering the body.

Answer

Enhanced for loop

Answer

while loop

Answer

for loop

Question 4

A method receives an int parameter and modifies its value inside the method. Does this change affect the caller's argument?

Accepted Answer

No, because Java passes a copy of the value. Java uses pass-by-value for all parameters. When an int is passed to a method, a copy of the value is made, so modifications inside the method affect only the copy, not the original variable in the caller's scope.

Answer

No, unless the parameter is marked as volatile

Answer

Yes, because the parameter is an int

Answer

Yes, because Java passes a reference

Question 5

Given int[] arr = {1,2,3}; which correctly creates a new array with length 5 and copies the contents of arr?

Accepted Answer

int[] newArr = Arrays.copyOf(arr, 5);. `Arrays.copyOf(int[] original, int newLength)` creates a new array of the specified length (5) and copies the elements from the original array into it, padding with default values (0 for int) for any extra positions. This method is specifically designed for this task, ensuring the original array remains unchanged.

Answer

int[] newArr = new int[5]; newArr = arr;

Answer

int[] newArr = arr.clone(); newArr.length = 5;

Answer

int[] newArr = Arrays.copy(arr, 5);

Question 6

A class defines two methods with the same name but different parameter lists. This is known as:

Accepted Answer

Method overloading. Method overloading occurs when a class defines multiple methods with the same name but different parameter lists (different number, type, or order of parameters). This is a compile-time polymorphism mechanism in Java that allows a method to handle different inputs without changing its name.

Answer

Method overriding

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Method hiding

Answer

Method shadowing

Question 7

Which access modifier allows members to be accessed only by classes in the same package?

Accepted Answer

default (no modifier). In Java, the default (package-private) access modifier, which is applied when no explicit modifier is used, restricts member access to only classes within the same package. This is the only access level that provides package-level visibility without inheritance or subclass access.

Answer

protected

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private

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public

Question 8

A subclass overrides a method from its superclass. Which annotation should be used to indicate the overriding intention?

Accepted Answer

The @Override annotation is optional but recommended. The @Override annotation is optional in Java; the compiler will still enforce method overriding without it. However, it is strongly recommended because it provides a compile-time check that the method correctly overrides a superclass method, preventing accidental overloading or typos in the method signature.

Answer

The @Override annotation is not allowed

Answer

The @Override annotation is used for overloading

Answer

The @Override annotation is mandatory

Question 9

Which TWO are valid Java identifiers? (Choose two.)

Accepted Answer

$test. ($test) is a valid Java identifier because identifiers can begin with a dollar sign ($) or an underscore (_), followed by any combination of letters, digits, dollar signs, or underscores. The Java Language Specification (JLS §3.8) explicitly allows the dollar sign as a starting character, though it is conventionally reserved for mechanically generated names.

Answer

class

Answer

my-var

Answer

2ndVar

Question 10

Which TWO statements about constructors are true? (Choose two.)

Accepted Answer

Constructors have no return type. Constructors in Java do not have a return type, not even void. If a return type is specified, the Java compiler treats the method as a regular method, not a constructor. This is a fundamental syntactic rule defined in the Java Language Specification (JLS §8.8).

Answer

The compiler always provides a default constructor

Answer

Constructors can be declared as abstract

Answer

Constructors have a return type of void

Question 11

Which THREE are primitive data types in Java? (Choose three.)

Accepted Answer

int. `int` is a primitive data type in Java that stores 32-bit signed integer values. Primitive types are predefined by the language and are not objects, meaning they are stored directly on the stack for efficiency.

Answer

String

Answer

Object

Question 12

Refer to the exhibit. What is the output?

Accepted Answer

int. The code performs an integer division because the double y is cast to int, making both operands int. The result is an int value of 2. The method typeOf(int) is called, which prints the string 'int'.

Answer

double

Answer

Runtime error

Answer

Compilation error

Question 13

Refer to the exhibit. What is the result of attempting to compile and run the code?

Accepted Answer

Compilation error because x is private in A. The code fails to compile because class B attempts to access the private field `x` of class A from a different class. In Java, private members are only accessible within the same class, not from subclasses or other classes, even if they are in the same file. The `super.x` reference in class B is illegal, causing a compilation error.

Answer

Prints 0

Answer

Runtime error

Answer

Prints 5

Question 14

Refer to the exhibit. What is the output?

Accepted Answer

String. The code exhibits method overloading with one method accepting an Object parameter and another accepting a String parameter. When a String argument is passed, Java selects the most specific matching method, which is the String version, so the output is 'String'.

Answer

Runtime error

Answer

Compilation error

Answer

Object

Question 15

A developer writes: int x; System.out.println(x); What is the result?

Accepted Answer

Compilation fails. B is correct because in Java, a local variable (such as `int x;` declared inside a method) must be initialized before it is used. The code attempts to print `x` without assigning a value, which violates the definite assignment rule and causes a compilation error.

Answer

null

Answer

Runtime error

Answer

0