1Z0-811 Java Basics and Syntax Practice Test 6 — 15 Questions

Question 1

A method is expected to receive an integer and return its square. Which method signature is correct?

Accepted Answer

int square(int x) { return x*x; }. The method signature specifies a return type of 'int' and includes the 'return' keyword to return the squared value. In Java, a method that returns a value must declare the return type before the method name and must use the 'return' statement to send the result back to the caller.

Answer

void square(int x) { return x*x; }

Answer

public square(int x) { return x*x; }

Answer

int square(int x) { x*x; }

Question 2

A developer writes: if (x = 5) { System.out.println("x is 5"); } What is the result?

Accepted Answer

Compilation error. In Java, the assignment operator `=` is used for assignment, not comparison. The expression `x = 5` assigns the value 5 to variable `x` and returns the assigned value (5). Since the condition in an `if` statement must be a boolean expression, and `int` cannot be implicitly converted to `boolean`, the compiler throws a compilation error. This is a fundamental syntax rule in Java, unlike in C/C++ where such an assignment would be allowed as a truthy check.

Answer

Prints "x is 5" if x equals 5

Answer

No output

Answer

Prints "x is 5" always

Question 3

Which TWO statements are true about the main method?

Accepted Answer

It must be declared public.. Option B is correct because the JVM launches the entry point of a Java application by invoking the main method with public visibility, so it must be declared public; otherwise, the runtime cannot access it and throws a NoSuchMethodError. Option D is correct because main must be declared static so the JVM can call it without instantiating the enclosing class. The full required signature is public static void main(String[] args). Option A is wrong because final is not required and has no role in the JVM's entry-point lookup. Option C is wrong because main must return void, not int. Option E is wrong because main can be overloaded (for example, main(int x) is legal); only the standard signature serves as the entry point.

Answer

It must be declared final.

Answer

It must return an int.

Answer

It cannot be overloaded.

Question 4

Which TWO are valid ways to create a String object?

Accepted Answer

String s = "hello";. Option C is correct because a string literal such as "hello" is interned in the string pool and directly creates/assigns a String object, which is the standard literal initialization form. Option E is correct because calling the String constructor with a String argument, new String("hello"), explicitly allocates a new String object (a distinct instance from the interned literal). Option A is incorrect because assigning null only sets the reference to no object; it does not create a String object. Option B is incorrect because String has no constructor accepting a single int (there is no new String(10) constructor), so it does not compile. Option D is incorrect because single quotes denote a char literal in Java, and 'hello' is not a valid char (and char cannot be assigned to String without conversion).

Answer

String s = null;

Answer

String s = new String(10);

Answer

String s = 'hello';

Question 5

Given the following code:

class A {
    A() { System.out.print("A "); }
}
class B extends A {
    B() { System.out.print("B "); }
}
class C extends B {
    C() { System.out.print("C"); }
    public static void main(String[] args) {
        new C();
    }
}

What is the output when running the main method?

Accepted Answer

A B C. In Java, when an object of a subclass is created, constructors are executed from the topmost superclass down to the subclass. Assuming the exhibit shows class C extends B extends A, with each constructor printing its class name, the output will be A B C.

Answer

B A C

Answer

A C B

Answer

C B A

Question 6

A developer writes the following code to compare two strings:
String s1 = "Java";
String s2 = new String("Java");
if (s1 == s2) { System.out.println("Equal"); } else { System.out.println("Not equal"); }
What is the output?

Accepted Answer

Not equal. The == operator compares object references, not the actual string content. Variable s1 refers to a string literal from the string pool, while s2 is a new String object created on the heap, so they are different objects and the comparison returns false, printing 'Not equal'.

Answer

Compilation error

Answer

Equal

Answer

Runtime error

Question 7

A package named com.example.util is declared in a file. Where should the file be placed in the directory structure?

Accepted Answer

com/example/util/. Java requires that the directory structure of a package matches the package declaration. A package named `com.example.util` must be stored in a directory hierarchy `com/example/util/` so that the Java compiler and runtime can locate the class files based on the fully qualified name. This ensures that the file is accessible via the classpath or module path.

Answer

com.example.util/

Answer

util/

Answer

com/example/util.java

Question 8

A developer uses the following array initialization:
int[] nums = new int[]{1, 2, 3};
Which of the following is true?

Accepted Answer

The array has length 3.. The array initialization `int[] nums = new int[]{1, 2, 3};` explicitly creates an array of length 3, containing the elements 1, 2, and 3. The syntax is valid and the array is not initialized with default values; it is initialized with the specified literal values.

Answer

This is invalid syntax.

Answer

The array is initialized with default values.

Answer

The array can only store numbers up to 3.

Question 9

A method is declared as:
public void setAge(int age) { this.age = age; }
Which statement is correct about this code assuming the class has an instance variable age?

Accepted Answer

The method sets the instance variable age.. The method `setAge(int age)` uses the `this` keyword to assign the parameter value to the instance variable `age`, which is a standard setter pattern in Java. The method has a `void` return type and is not a constructor, and it compiles successfully because the instance variable `age` is assumed to exist in the class.

Answer

The method is a constructor.

Answer

The method will cause a compilation error.

Answer

The method is static.

Question 10

A developer writes the following code: int x = 5; int y = x++; What are the values of x and y after execution?

Accepted Answer

x = 6, y = 5. The post-increment operator `x++` returns the original value of `x` (5) before incrementing. Therefore, `y` is assigned 5, and `x` becomes 6 after the increment. This is a fundamental behavior of post-increment in Java.

Answer

x = 5, y = 5

Answer

x = 5, y = 6

Answer

x = 6, y = 6

Question 11

Which data type should be used to store a single character like 'A'?

Accepted Answer

char. In Java, the `char` data type is a single 16-bit Unicode character, capable of storing any character from the Unicode standard, including 'A'. It is the primitive type specifically designed for a single character, whereas `String` is a reference type for sequences of characters.

Answer

String

Answer

byte

Answer

int

Question 12

Given: int[] arr = {10,20,30}; System.out.println(arr[3]); What is the result?

Accepted Answer

ArrayIndexOutOfBoundsException. Arrays in Java are zero-indexed, so a valid index for an array of length 3 is 0, 1, or 2. Accessing index 3 is out of bounds, causing an ArrayIndexOutOfBoundsException at runtime.

Answer

30

Answer

0

Answer

NullPointerException

Question 13

Which method overloading is valid?

Accepted Answer

void print(int a) and void print(String s) {}. Method overloading in Java requires methods to have the same name but different parameter lists (different number, type, or order of parameters). Here, `void print(int a)` and `void print(String s)` have different parameter types (`int` vs `String`), which satisfies the overloading rule. The return type or access modifiers do not affect overloading.

Answer

void print(int a) and void print(int b) {}

Answer

void print(int a) and int print(int a) {}

Answer

void print(int a) and private void print(int a) {}

Question 14

What is the scope of a variable declared inside a for loop?

Accepted Answer

Only inside the loop block. In Java, a variable declared inside a for loop (including the initialization block or the loop body) has block scope, meaning it is only accessible within the loop block itself. This is defined by the Java Language Specification (JLS §6.10), which states that the scope of a local variable declaration is the rest of the block in which the declaration appears. Once the loop completes, the variable goes out of scope and cannot be referenced.

Answer

Inside the package

Answer

Inside the class

Answer

Inside the entire method

Question 15

Which TWO keywords are used to control access to class members? (Choose two.)

Accepted Answer

private. The question asks for keywords that control access to class members, i.e., access modifiers. Option A, private, is correct because it restricts a member's visibility to the declaring class only, preventing access from subclasses or other classes. Option C, public, is correct because it grants unrestricted access to a member from any other class in any package. The other options do not control access: static (B) controls whether a member belongs to the class rather than instances, abstract (D) declares that a method has no implementation or that a class cannot be instantiated, and final (E) prevents reassignment, overriding, or inheritance.

Answer

static

Answer

abstract

Answer

final