1Z0-811 Primitives, Strings and Operators Practice Test 2 — 15 Questions

Question 1

Which primitive type can store a single character?

Accepted Answer

char. The `char` primitive type in Java is specifically designed to store a single 16-bit Unicode character, ranging from '\u0000' (0) to '\uffff' (65535). It is the only primitive type that directly represents a character value, making it the appropriate choice for storing a single character.

Answer

String

Answer

byte

Answer

short

Question 2

Given: double d = 5.0; int i = d; What is the result?

Accepted Answer

Compilation fails. In Java, assigning a double to an int without an explicit cast causes a compilation error because double is a 64-bit floating-point type and int is a 32-bit integer type. Java does not allow implicit narrowing conversions due to potential loss of precision, so the code fails to compile.

Answer

5.0

Answer

5

Answer

Runtime error

Question 3

What is the default value of a boolean variable in Java?

Accepted Answer

false. In Java, the default value of a boolean variable (when declared as a class field or instance variable) is 'false'. This is specified by the Java Language Specification (JLS §4.12.5), which defines default values for all primitive types. Unlike local variables, which must be explicitly initialized, instance and static variables receive default values automatically.

Answer

null

Answer

true

Answer

0

Question 4

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 5

Which THREE of the following are valid Java operators?

Accepted Answer

<<. (<<) is correct because it is the Java left shift operator, which shifts the bits of an integer or long value to the left by a specified number of positions, filling with zeros. This is a valid bitwise shift operator in Java, defined in the Java Language Specification (JLS §15.19).

Answer

::

Answer

<==

Question 6

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

Accepted Answer

double. (double) is correct because double is a 64-bit IEEE 754 floating-point primitive data type in Java, used for decimal values with double precision. Option D (int) is correct because int is a 32-bit signed two's complement integer primitive, the default integer type in Java. Both are part of the eight primitive types defined in the Java Language Specification.

Answer

String

Answer

Integer

Answer

Boolean

Question 7

Which THREE of the following expressions evaluate to true? (Assume int a=5, b=10)

Accepted Answer

a < b. The expression 'a < b' compares the integer values of a (5) and b (10). Since 5 is less than 10, the relational operator '<' returns the boolean value true.

Answer

a == b

Answer

a >= b

Question 8

What is the value of y after executing the following code?
```java
int y = 10 + 12;
```

Accepted Answer

22. The code snippet `int y = 10 + 12;` performs integer addition, resulting in y = 22. Java's primitive arithmetic follows standard rules, so adding 10 and 12 yields 22 without any overflow or conversion issues.

Answer

20

Answer

21

Answer

23

Question 9

A developer is working on a Java application that processes user input. The application reads a string from the console and needs to compare it with a predefined constant string "ADMIN". The developer writes the following code: if (input == "ADMIN") { grantAccess(); }. During testing, the condition sometimes fails even when the user enters ADMIN. The input string is obtained via Scanner.nextLine(). Which is the most likely cause and best fix?

Accepted Answer

Use input.equals("ADMIN") instead of ==.. `==` compares object references, not string content. `Scanner.nextLine()` returns a new `String` object, so `input == "ADMIN"` compares references, which are different even if the content matches. Using `input.equals("ADMIN")` compares the actual character sequence, which is the correct way to test string equality in Java.

Answer

Use input.compareTo("ADMIN") == 0.

Answer

Use input == "ADMIN" with intern() on input.

Answer

Convert input to char array and compare.

Question 10

A banking application uses a method to calculate interest: double calculateInterest(double balance) { return balance * 0.05; }. The method is called with an int argument: int accountBalance = 1000; double interest = calculateInterest(accountBalance); System.out.println(interest); The output is 50.0, but the expected output is 50.0. However, the developer notices that if the method is changed to return int, the output becomes 50.0 as well. Which statement about implicit casting is true?

Accepted Answer

The int argument is implicitly cast to double.. When a method expecting a `double` parameter is called with an `int` argument, Java performs implicit widening primitive conversion (casting) from `int` to `double`. This is safe because `double` can represent all `int` values without loss of precision. The `int` value 1000 is automatically converted to `1000.0` before being used in the calculation.

Answer

The double result is implicitly cast to int.

Answer

The code fails to compile because of type mismatch.

Answer

The multiplication result is automatically rounded.

Question 11

A developer writes the following code:

int a = 5;
int b = 2;
double result = a / b;
System.out.println(result);

What is the output?

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, a (5) divided by b (2) yields 2, and then the result is implicitly widened to double when assigned to the variable result, producing 2.0.

Answer

2.5

Answer

Compilation fails

Answer

2

Question 12

Arrange the steps to handle an exception using try-catch-finally in Java in the correct order.

Accepted Answer

try block, then catch block, then finally block. The try block contains risky code, catch handles the exception, and finally executes cleanup. The order is try, catch, then finally.

Answer

catch block, then try block, then finally block

Answer

finally block, then try block, then catch block

Answer

try block, then finally block, then catch block

Question 13

Arrange the steps to create and use a simple Java inheritance hierarchy in the correct order.

Accepted Answer

Create the superclass, then create the subclass with extends, then override methods if needed, then add new members, then use the subclass.. First create the superclass, then create subclass with extends, override methods if needed, add new members, and then use the subclass.

Answer

Create the subclass, then create the superclass, then override methods, then add new members, then use the subclass.

Answer

Create the superclass, then create the subclass with extends, then add new members, then override methods, then use the subclass.

Answer

Create the superclass, then create the subclass without using extends (copy code), then override methods, then add new members, then use the subclass.

Question 14

Match each Java tool to its function.

Accepted Answer

javac: Compiles Java source code into bytecode. The correct matches are: javac compiles source code, java runs applications, javadoc generates documentation, and jar creates archives. Common confusions involve mixing up javac with jar and java with javadoc.

Answer

javac: Packages class files into an archive

Answer

java: Generates API documentation

Question 15

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

Accepted Answer

true. String literals in Java are interned, meaning both s1 and s2 refer to the same String object in the string constant pool. The == operator compares object references, not content, so since both variables point to the same interned string, the comparison yields true.

Answer

Compilation fails

Answer

false

Answer

Hello