1Z0-811 Practice Test 3 — 30 Questions

Question 1

Given the code snippet: 'int[] nums = {10, 20, 30, 40}; int sum = 0; for (int i = 0; i < nums.length; i++) { sum += nums[i]; }'. What is the value of sum after execution?

Accepted Answer

100. (100) because the for loop iterates over each element of the array {10, 20, 30, 40} and adds it to the sum variable. The sum starts at 0, and after adding 10, 20, 30, and 40, the total becomes 100.

Answer

30

Answer

60

Answer

140

Question 2

A method 'public static void modify(int[][] matrix) { matrix[0][0] = 99; }' is called with 'int[][] values = {{1,2},{3,4}}; modify(values);'. What is the value of values[0][0] after the call?

Accepted Answer

99. Java passes object references by value. When 'modify(values)' is called, the reference to the 2D array is copied into the method parameter 'matrix'. Since 'matrix' points to the same array object, modifying 'matrix[0][0]' directly changes the original array's element, so 'values[0][0]' becomes 99.

Answer

Exception

Answer

1

Answer

0

Question 3

Given the code:

int[] a = {1, 2, 3};
int[] b = {4, 5};
a = b;
b[0] = 99;
System.out.println(a[0]);

What is the output?

Accepted Answer

99. After `a = b;`, both `a` and `b` reference the same array object. Modifying `b[0]` to 99 also changes `a[0]` because they share the same underlying array. Therefore, `a[0]` prints 99.

Answer

3

Answer

1

Answer

4

Question 4

Which TWO methods correctly modify the passed array in place?

Accepted Answer

public void zeroOut(int[] a) { for (int i = 0; i < a.length; i++) a[i] = 0; }. It directly modifies each element of the passed array by assigning 0 to a[i] within the loop. In Java, when an array is passed to a method, the method receives a reference to the same array object, so changes to the array's elements are reflected in the caller's array.

Answer

public void reset(int[] a) { a = new int[10]; }

Answer

public void swap(int[] a) { int[] temp = a; a = new int[1]; a[0] = temp[0]; }

Answer

public void setFirst(int[][] a) { a = new int[1][1]; a[0][0] = 5; }

Question 5

A developer needs to store a currency value with two decimal places. Which primitive type is most appropriate?

Accepted Answer

double. (double) is the most appropriate primitive type for storing a currency value with two decimal places because double is a 64-bit IEEE 754 floating-point type that can represent fractional values with sufficient precision for typical monetary amounts. While float (32-bit) could also store decimals, double provides higher precision (15-16 significant digits) and is the default type for decimal literals in Java, making it the standard choice for currency calculations in the exam context.

Answer

float

Answer

long

Answer

int

Question 6

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 7

A developer writes a method that reads a file and must ensure the file is closed even if an exception occurs. Which construct should be used?

Accepted Answer

A try-with-resources statement. The try-with-resources statement automatically closes any resource that implements `AutoCloseable` (such as `FileReader` or `BufferedReader`) at the end of the statement, even if an exception occurs. This eliminates the need for explicit cleanup code and ensures deterministic resource management without relying on a `finally` block.

Answer

A throws declaration in the method signature

Answer

A finally block without any resource declaration

Answer

A try-catch-finally block with explicit close in finally

Question 8

Consider the following code snippet: 
public int getValue() {
    try {
        return 1;
    } catch (Exception e) {
        return 2;
    } finally {
        return 3;
    }
}
What does the method return?

Accepted Answer

3. (3) because a `finally` block always executes after the `try` block, and if the `finally` block contains a `return` statement, that return value overrides any return value from the `try` or `catch` blocks. In Java, the `finally` block's `return` statement causes the method to exit with the value 3, regardless of what the `try` block attempted to return.

Answer

The code does not compile.

Answer

2

Answer

1

Question 9

What does the java command with -jar option do?

Accepted Answer

Executes a JAR file by reading its manifest. The `java -jar` command executes a JAR file by reading the `Main-Class` entry from the JAR's manifest file (`META-INF/MANIFEST.MF`). This tells the Java launcher which class contains the `public static void main(String[] args)` method to start the application. It does not compile, list, or create JAR files.

Answer

Compiles Java files inside the JAR

Answer

Lists contents of the JAR file

Answer

Creates a new JAR file

Question 10

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

Accepted Answer

double. `double` is one of the eight primitive data types in Java, used to store floating-point numbers with double precision (64-bit IEEE 754). It is a fundamental type that holds a numeric value directly, not an object reference.

Answer

String

Answer

array

Question 11

Given: byte b = 10; b = b + 1; Which statement is true?

Accepted Answer

Compilation error because byte cannot be assigned int.. In Java, the expression `b + 1` performs binary numeric promotion, widening the `byte` operand to `int` before addition. The result is an `int` (11), which cannot be implicitly assigned back to a `byte` variable without a cast. Therefore, `b = b + 1;` causes a compilation error: 'incompatible types: possible lossy conversion from int to byte'. Option C correctly identifies this error.

Answer

The value of b becomes 11.

Answer

b is automatically widened to int then assigned back without error.

Answer

The expression b+1 results in a byte.

Question 12

Which two of the following are primitives in Java? (Choose two.)

Accepted Answer

byte. A is correct because `byte` is a primitive data type in Java that stores 8-bit signed integers, ranging from -128 to 127. It is one of the eight primitive types defined in the Java language specification, not an object or reference type.

Answer

String

Answer

Integer

Answer

Boolean

Question 13

What is the output of the following? int x = Integer.MAX_VALUE; x++; System.out.println(x);

Accepted Answer

-2147483648. When x is Integer.MAX_VALUE (2147483647) and incremented, integer overflow occurs because Java int uses 32-bit two's complement representation. The value wraps around to the minimum int value, which is -2147483648, making D correct.

Answer

2147483647

Answer

0

Answer

Exception

Question 14

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

Accepted Answer

double. `double` is one of the eight primitive data types in Java, used to represent double-precision 64-bit IEEE 754 floating-point numbers. Primitives are predefined by the language and stored directly in stack memory, not as objects.

Answer

Integer

Answer

String

Question 15

A developer writes a switch statement that checks the day of the week. The code uses fall-through to handle weekdays. What happens if a case does not end with a break?

Accepted Answer

Execution continues to the next case. In Java, when a case in a switch statement does not end with a break statement, execution falls through to the next case, continuing until a break is encountered or the switch block ends. This is known as fall-through behavior, which the developer intentionally uses to handle weekdays collectively.

Answer

The default case is executed

Answer

Compilation error

Answer

Runtime exception is thrown

Question 16

Which TWO access modifiers allow access from a subclass in a different package?

Accepted Answer

protected. (protected) is correct because the protected access modifier allows access to members of a superclass by subclasses in different packages, provided the subclass inherits from the superclass. Option E (public) is also correct because public members are accessible from any class, regardless of package or inheritance.

Answer

private

Answer

static

Answer

default (no modifier)

Question 17

A method is declared as: public static void main(String[] args) { }. Which statement is true?

Accepted Answer

The method can be called without creating an instance of the class.. The `static` modifier in the method signature means the method belongs to the class itself, not to any instance. Therefore, it can be invoked using the class name (e.g., `ClassName.main(args)`) without creating an object of the class. This is a fundamental characteristic of static methods in Java.

Answer

The method can be overridden in a subclass.

Answer

The method can return an int.

Answer

The method can be private.

Question 18

Which primitive type has a default value of 0.0f?

Accepted Answer

float. In Java, the default value for a float primitive is 0.0f. This is because float is a 32-bit IEEE 754 floating-point type, and its default initialization is 0.0f (with the 'f' suffix to denote a float literal). Option A is correct because it directly matches this specification.

Answer

long

Answer

double

Answer

int

Question 19

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 20

Which THREE of the following statements about operators in Java are true?

Accepted Answer

The instanceof operator can be used to check if an object is an instance of a class.. The `instanceof` operator in Java is a binary operator used to test whether an object is an instance of a specific class, subclass, or interface. It returns `true` if the object is an instance of the specified type, otherwise `false`, and is commonly used for type checking before casting.

Answer

The right shift operator (>>) always fills with zeros.

Answer

The equality operator (==) compares the content of objects.