1Z0-811 Practice Test 35 — 15 Questions

Question 1

A developer needs to store whether a customer has opted in to marketing emails. The value will be either true or false, and the field will later be compared inside conditional statements. Which declaration is most appropriate for this field?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

boolean optedIn;. A yes/no flag maps naturally onto the boolean primitive, which is the only Java type that accepts true and false and can be used directly in conditional expressions. Substituting String, int, or char forces an encoding convention that the compiler cannot enforce and that permits invalid states. The boolean declaration is therefore the clearest and safest choice.

Answer

int optedIn;

Answer

char optedIn;

Answer

String optedIn;

Question 2

A developer is writing a utility method that opens a file, reads all lines, and returns the contents. The method should automatically close the file even if an exception occurs during reading. Which Java construct is specifically designed for this requirement?

Accepted Answer

A `try-with-resources` statement that declares the file reader in the resource specification.. `try-with-resources` is the construct designed to close resources automatically at the end of the statement, whether execution completes normally or throws an exception. The resource must implement `AutoCloseable`. Manual `finally` cleanup works but is not the purpose-built feature, and the other options do not close file handles at all.

Answer

A `catch` block that calls `System.gc()` to release the file handle.

Answer

A `try` block with a `finally` block that calls `close()` manually.

Answer

A `synchronized` block that prevents other threads from accessing the file.

Question 3

A university student installs the JDK on a Windows laptop and wants to compile and run a simple HelloWorld.java file from the command line without using an IDE. After compilation, which command should the student use to execute the program?

Accepted Answer

java HelloWorld. After source code is compiled with javac, the resulting bytecode is executed by the java launcher using the class name only, without the .class extension. The java command starts the JVM, locates the class on the class path, and invokes its main method. This is the fundamental compile-then-run workflow for Java SE applications.

Answer

java HelloWorld.java

Answer

run HelloWorld.class

Answer

javac HelloWorld

Question 4

A developer writes a method that receives an int array and intends to reverse its contents in place. Inside the method the parameter is reassigned to a newly created array holding the reversed values. After the method returns, the caller's original array is unchanged. Why?

Accepted Answer

Java passes object references by value, so reassigning the parameter does not affect the caller's reference. Java is strictly pass-by-value. When an array is passed, the method receives a copy of the reference. Writing to elements through that copy changes the shared array object and is visible to the caller, but reassigning the parameter to a brand-new array merely repoints the local copy. The caller's variable still references the original, unmodified array.

Answer

Arrays in Java are immutable once created, so no method can change their contents

Answer

Arrays are passed by reference, so the reassignment should have changed the caller's array but did not due to a compiler bug

Answer

The method must declare the parameter as final to allow in-place modification

Question 5

A developer is writing a method that calculates the average of two integers and wants the result to include fractional values. The method signature is:

public static double average(int a, int b)

Which return statement produces the intended result?

Accepted Answer

return (a + b) / 2.0;. To obtain a fractional average, at least one operand of the division must be a floating-point value so binary numeric promotion converts the other operand. Using the double literal 2.0 forces the int sum to widen before division. Grouping the addition with parentheses is also necessary, since division has higher precedence than addition.

Answer

return a + b / 2;

Answer

return (double) (a + b / 2);

Answer

return (a + b) / 2;

Question 6

A developer needs to store the number of active users in a web application. The value will be a whole number and will never exceed 2 billion. Which primitive data type is most appropriate for this purpose?

Accepted Answer

int. The int primitive type is designed for 32-bit signed whole numbers and covers the range up to about 2.1 billion. Since the user count will never exceed 2 billion, int provides sufficient capacity without wasting memory. Other integral types like short are too small, long is overkill, and float is inappropriate for exact counting because it represents decimal values with limited precision.

Answer

float

Answer

short

Answer

long

Question 7

A developer writes a class named Shape with a method area that returns a double. A subclass named Circle overrides area to compute the circle's area. A variable of type Shape is assigned a new Circle object, and area is invoked on that variable. Which statement correctly describes how the method call is resolved?

Accepted Answer

The Circle version of area executes because the object's actual type is Circle.. Java resolves overridden instance methods at runtime using the class of the actual object. The reference type Shape only governs compile-time visibility of members. Because the instance is a Circle, Circle's area implementation is invoked. Java never executes both versions automatically; a superclass implementation runs only through an explicit super call.

Answer

The Shape version of area executes because the variable's declared type is Shape.

Answer

Compilation fails because Shape's area cannot be called through a Shape reference to a Circle object.

Answer

Both versions execute in sequence, with Shape's area first and then Circle's area.

Question 8

A developer writes the following code:

public class Test {
    public static void main(String[] args) {
        try {
            throw new RuntimeException("A");
        } catch (Exception e) {
            System.out.print("B");
        } finally {
            System.out.print("C");
        }
    }
}

What is printed?

Accepted Answer

BC. The thrown RuntimeException is a subclass of Exception, so the catch block handles it and prints B. The finally block executes regardless of whether an exception is caught, printing C. The exception message "A" is never printed. Thus the program outputs BC.

Answer

C

Answer

B

Answer

ABC

Question 9

A developer uses the javadoc tool to generate documentation for a package. The source files contain Javadoc comments with the @param tag for a method parameter, but the generated HTML does not show the parameter description. The method signature is: public void calculate(int value). Which is the most likely cause?

Accepted Answer

The @param tag is missing the parameter name or the parameter name does not match the method signature.. The @param tag must include the exact parameter name followed by a description. If the name is missing or does not match the method signature, javadoc cannot associate the description with the parameter, so it is omitted from the generated HTML. Ensuring the parameter name matches exactly resolves the issue.

Answer

The method is not public, so javadoc by default does not generate documentation for its parameters.

Answer

The @param tag must be placed immediately before the method declaration, not inside the method body.

Answer

The javadoc tool does not support the @param tag for methods with a single parameter.

Question 10

A developer writes the following code to categorize a temperature reading:

```java
int t = 32;
if (t < 0)
    System.out.print("Freezing ");
if (t < 32)
    System.out.print("Cold ");
else
    System.out.println("Mild");
```

What is printed?

Accepted Answer

Mild. The two if statements are independent; the first has no else and simply does nothing when its condition is false. With t equal to 32, the test t < 0 fails, and the test t < 32 also fails because the comparison is strict. Control therefore falls to the else attached to the second if, which prints Mild on its own line.

Answer

Freezing Mild

Answer

Cold

Answer

Freezing Cold

Question 11

A start-up is choosing a Java platform for a new customer-facing web application. The team needs the full standard class library plus the ability to serve HTTP requests directly and deploy packaged web components, while still writing plain Java code with no proprietary vendor APIs. Which Java platform edition should they select?

Accepted Answer

Java EE (Jakarta EE). The enterprise edition is defined as a superset of the standard edition that standardizes server-side APIs, including web containers for servlets and packaged web components. Because those APIs are specifications rather than proprietary vendor interfaces, code written against them stays portable. Java SE alone lacks web-hosting APIs, Java ME targets constrained devices, and JavaFX is a desktop UI toolkit.

Answer

Java ME

Answer

JavaFX

Answer

Java SE

Question 12

A developer is reviewing code that iterates over a one-dimensional int array named readings using a standard for loop. The loop must access every element exactly once without any out-of-bounds errors. Which loop condition should be used?

Accepted Answer

i < readings.length. Because Java array indexes begin at zero, the highest valid index for any array is its length minus one. A loop that continues while the index is strictly less than the array length therefore touches every element exactly once and stops precisely before the first invalid index, making it the safe and conventional choice for full traversal.

Answer

i <= readings.length - 1

Answer

i <= readings.length

Answer

i < readings.length - 1

Question 13

A developer runs a Java application and sees the message `Exception in thread "main" java.lang.ArithmeticException: / by zero` followed by a stack trace. Which statement best describes what happened?

Accepted Answer

The exception propagated out of the main method uncaught, so the default handler printed the stack trace and the thread terminated.. The prefix `Exception in thread "main"` is the signature of the JVM's default uncaught exception handler. It indicates that the ArithmeticException traveled up the call stack without being caught and reached the top of the main thread. The thread then terminates, and because main is the last non-daemon thread, the JVM shuts down.

Answer

The exception was thrown by the operating system because the process ran out of memory.

Answer

The compiler detected the division by zero and generated the message during compilation.

Answer

The exception was caught by a handler in the main method, which printed the message.

Question 14

A developer is reviewing a class that declares several variables at different scopes. The class has an instance field named count, and a method contains a local variable also named count. The developer needs to identify which statements about variable scope and shadowing in Java are correct. (Choose two.)

Accepted Answer

An instance field is accessible from any method of the same class regardless of declaration order.. Local variables live only inside the block where they are declared, so they vanish at the closing brace, while instance fields are members of the object and are reachable from every non-static method of the class regardless of where they appear in the source file. Shadowing a field with a same-named local variable is legal and simply hides the field until the local scope ends.

Answer

A static method can directly access an instance field of its own class without an object reference.

Answer

A local variable with the same name as an instance field causes a compilation error.

Answer

A variable declared inside a for loop header remains accessible after the loop terminates.

Question 15

A developer compiles a Java source file with the command `javac -d classes src/com/example/App.java`. The compilation succeeds. Where is the resulting `App.class` file placed?

Accepted Answer

In `classes/com/example/App.class`, with the package directory structure created under `classes`.. When javac is invoked with -d, it treats the argument as the root of the output directory tree and mirrors the package name as subdirectories. For a source file declaring package com.example, the compiler creates classes/com/example and writes App.class inside it, keeping the class file location consistent with the fully qualified class name.

Answer

In `src/com/example/App.class`, alongside the source file.

Answer

In the current working directory.

Answer

In `classes/App.class`, directly under `classes` without package subdirectories.