1Z0-811 Java Basics and Syntax Practice Test 5 — 15 Questions

Question 1

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

Accepted Answer

$test. Option A ($test) is a valid Java identifier because the dollar sign ($) is a legal identifier-start character in Java, alongside letters, the underscore, and Unicode letter characters, so an identifier may begin with $. Option D (_myVar) is also valid because the underscore (_) is an allowed identifier-start character and the remaining characters are letters, making it a well-formed Java identifier. Option B (class) is not valid because class is a reserved Java keyword and cannot be used as an identifier. Option C (my-var) is invalid because the hyphen (-) is not a legal Java identifier character; only letters, digits, $, and _ are permitted. Option E (2ndVar) is invalid because a Java identifier cannot begin with a digit, even though digits are allowed after the first character.

Answer

class

Answer

my-var

Answer

2ndVar

Question 2

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

Accepted Answer

Constructors have no return type. Option A is correct because a constructor is declared without any return type — not even void — since its purpose is only to initialize a new object, and the JVM treats it specially during object creation. Option C is correct because the compiler implicitly inserts a no-argument default constructor only when the class defines no constructors at all; as soon as any constructor is declared, no default is generated. Option B is wrong because the compiler does not "always" provide a default constructor — it is suppressed once any constructor is explicitly defined. Option D is wrong because constructors cannot be abstract; they are never inherited or overridden, so abstract (which requires overriding) is illegal on a constructor. Option E is wrong because constructors have no return type whatsoever, and explicitly writing void would turn the declaration into a regular method rather than a constructor.

Answer

The compiler always provides a default constructor

Answer

Constructors can be declared as abstract

Answer

Constructors have a return type of void

Question 3

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

Accepted Answer

int. Option A (int) is correct because int is one of Java's eight built-in primitive types, representing a 32-bit signed two's-complement integer. Option B (boolean) is correct because boolean is a primitive type that holds only the values true or false, with a size defined by the JVM. Option D (double) is correct because double is a primitive type storing a 64-bit IEEE 754 double-precision floating-point value. Option C (String) is not a primitive; it is a reference type, specifically a final class in java.lang, and its literals are interned objects. Option E (Object) is also a reference type, the root class of the Java class hierarchy, not a primitive.

Answer

String

Answer

Object

Question 4

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 5

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

Question 6

Given: String s = "Java"; s.concat(" Rocks"); System.out.println(s); What prints?

Accepted Answer

"Java". Strings in Java are immutable. The `concat()` method returns a new string object but does not modify the original string `s`. Since the return value is not assigned to any variable, the original string `s` remains unchanged, so `System.out.println(s)` prints "Java".

Answer

"Rocks"

Answer

""

Answer

"Java Rocks"

Question 7

What is the result of: int[] arr = new int[5]; System.out.println(arr[5]);

Accepted Answer

ArrayIndexOutOfBoundsException. Java arrays are zero-indexed, meaning a valid index for an array of length 5 is 0 through 4. Accessing index 5 throws an ArrayIndexOutOfBoundsException at runtime, as it is outside the array's bounds.

Answer

null

Answer

-1

Answer

0

Question 8

Given: int day = 3; switch(day) { case 1: System.out.print("A"); case 2: System.out.print("B"); case 3: System.out.print("C"); case 4: System.out.print("D"); } What prints?

Accepted Answer

"CD". The switch statement does not have break statements, so after matching case 3, execution falls through to case 4, printing 'C' then 'D'. The output is 'CD'.

Answer

"BCD"

Answer

"C"

Answer

"ABCD"

Question 9

Given methods: void print(Integer i) { System.out.println("Integer"); } void print(int i) { System.out.println("int"); } What is output of print(10);?

Accepted Answer

"int". When calling print(10) with an integer literal, Java's method overloading resolution prefers the primitive int version over the Integer wrapper type because the literal 10 is a primitive int. The compiler selects the most specific matching method without requiring autoboxing, so the void print(int i) method is invoked, printing "int".

Answer

Compilation error

Answer

"Integer"

Answer

Runtime error

Question 10

Consider: for(int i=0;i<10;i++) { int x = i; } System.out.println(x); What is the result?

Accepted Answer

Compilation error. The variable `x` is declared inside the `for` loop block, so its scope is limited to that block. Attempting to use `x` outside the loop (in the `System.out.println(x);` statement) causes a compilation error because `x` is not in scope at that point. The Java compiler enforces block-level scoping rules, and any reference to a variable outside its declared block results in a 'cannot find symbol' error.

Answer

9

Answer

10

Answer

0

Question 11

Given method: static void change(String s) { s = "new"; } What is output of: String name = "original"; change(name); System.out.println(name);

Accepted Answer

"original". Java passes object references by value. Inside the method `change`, the local variable `s` is reassigned to a new String object, but this does not affect the original reference `name` in the main method. Strings are immutable, so the original `name` remains "original".

Answer

null

Answer

"new"

Answer

Compilation error

Question 12

What is the result of: Integer a = null; int b = (a != null) ? a : 0; System.out.println(b);

Accepted Answer

0. The ternary operator evaluates the condition (a != null). Since a is null, the condition is false, so the expression returns the second operand, which is the int literal 0. This value is assigned to int b, and System.out.println(b) prints 0. No NullPointerException occurs because the ternary operator never attempts to unbox a null reference.

Answer

NullPointerException

Answer

Compilation error

Answer

null

Question 13

Which TWO of the following are valid Java identifiers?

Accepted Answer

_count. Option C, _count, is a valid Java identifier because it begins with an underscore, which is a legal first character, and contains only letters and the underscore thereafter. Option E, $dollar, is also valid because the dollar sign is explicitly permitted as both a starting and subsequent character in Java identifiers. Option A, class, is invalid because it is a reserved Java keyword and cannot be used as an identifier. Option B, 2ndValue, is invalid because identifiers cannot begin with a digit. Option D, my-var, is invalid because the hyphen is not a legal identifier character in Java.

Answer

class

Answer

2ndValue

Answer

my-var

Question 14

Which THREE of the following are primitive data types in Java?

Accepted Answer

boolean. In Java, the primitive data types are the eight built-in value types defined by the language: byte, short, int, long, float, double, boolean, and char. Option B (boolean) is correct because it is a primitive type that holds only true or false values. Option C (int) is correct because it is a primitive 32-bit signed two's complement integer type. Option E (char) is correct because it is a primitive 16-bit Unicode character type. Option A (void) is not a data type at all; it is a keyword used only to indicate that a method returns no value. Option D (String) is not primitive because it is a reference type, specifically an instance of the java.lang.String class.

Answer

void

Answer

String

Question 15

Refer to the exhibit. What is the likely cause of this error?

Accepted Answer

x is declared but not initialized. In Java, a local variable must be explicitly initialized before it is used; otherwise, the compiler reports an 'error: variable x might not have been initialized'. The exhibit shows a compilation error, and the most likely cause is that x was declared (e.g., 'int x;') but never assigned a value before being referenced in an expression or printed.

Answer

x is out of scope

Answer

x is a duplicate variable

Answer

x is declared as a different type