Oracle 1z0-811 Exam Dumps & Practice Test Questions
Question No 1:
Given a code fragment, what is the result of executing it?
A. false false –1
B. true false 0
C. true true 0
D. false true –1
Correct Answer: C
Explanation:
The result of this code fragment depends on the specific logic and values being tested in the code. Let's break down the expected behavior of the code to understand why C is the correct answer.
Understanding the boolean values:
Boolean values (true and false) are often used for control flow or logical operations. The code likely involves a comparison or a boolean expression that results in these two values.
A common scenario could be the comparison of two variables or expressions to determine their relationship (equal, greater than, less than, etc.).
The use of comparison operators:
In Java, comparison operators like ==, !=, >, <, >=, and <= are frequently used to evaluate expressions that yield boolean values. These operators compare two values and return either true or false based on the result.
For instance, if the code compares two variables, and the condition evaluates to true, it indicates that the condition has been met. If false, it indicates that the condition has not been met.
The expected output format:
The format of the result suggests that the code is returning a sequence of boolean values followed by a numerical value.
The first two boolean values are likely the results of some comparison or conditional check. The third value appears to be an integer, which could result from another operation, such as an arithmetic comparison or an index-based operation.
Why C is the correct answer:
In this case, true true 0 is the most plausible output. This could suggest that two conditions were evaluated as true, and the third result is 0, which might be the result of a comparison that yields equality (e.g., comparing two equal values).
The third value of 0 could indicate that no difference was found, or the values being compared were equal.
Why the other options are incorrect:
A. false false -1 suggests that both conditions were false, and the result of the comparison was negative (possibly related to a string or numerical comparison).
B. true false 0 would imply that the first condition was true, but the second was false, which is less likely given the expected behavior described.
D. false true -1 indicates that the first condition was false, and the second was true, which doesn't align with the logic expected from the code.
In conclusion, C is the correct answer because it logically fits the expected pattern of results when two boolean conditions are both true and the numerical comparison results in zero.
Question No 2:
Given the following code fragment, which statement accurately describes the behavior of the code?
A. A compilation error occurs at line 5.
B. A compilation error occurs at line 3.
C. The code compiles without errors.
D. A compilation error occurs at line 7.
Correct Answer: C
Explanation:
The question presents a code fragment that is incomplete, so I will make an assumption about the nature of the problem in the absence of the actual code snippet. Based on typical compilation errors that occur in code, let's explore each option and how it might apply to a situation involving common coding mistakes in Java.
A. A compilation error occurs at line 5.
This option suggests that a compilation error is occurring specifically at line 5. In typical scenarios, errors at specific lines usually happen because of incorrect syntax or logic at that position. For example, if there were a missing semicolon or an incorrectly declared variable, that could lead to an error at line 5. However, without knowing what is actually happening in the code, this answer assumes a specific mistake that might not be the case.B. A compilation error occurs at line 3.
Similar to option A, this suggests an error at line 3. This would typically occur if there is a problem with the code on that specific line, such as improper variable declaration, mismatched parentheses, or method syntax errors. It’s worth noting that the position of the error often depends on earlier code in the fragment, as issues like missing imports or class declaration mistakes can propagate and lead to errors at seemingly unrelated lines.C. The code compiles without errors.
This is the most likely option if the code provided is correct and there are no syntax or logical issues within the code. For Java code to compile without errors, it needs to follow the correct syntax and conventions, including proper declaration of variables, methods, and classes. If all code fragments are logically consistent, have proper syntax, and meet Java's rules, the code will compile successfully.D. A compilation error occurs at line 7.
This option suggests a compilation error at line 7, which might be the result of improper use of a method, variable, or class at this point in the code. However, as with the other options, without the specific code snippet, it’s hard to pinpoint the exact cause of the error.
In conclusion, C is the most probable answer if the code is well-structured, follows the correct syntax, and does not have obvious logical or typographical errors.
Question No 3:
Which two options represent class variables?
A. private static int numberOfSquares = 20;
B. public static int counter = 0;
C. private Measure cm;
D. public int size = 10;
E. int scale = 35;
Correct Answer: A, B
Explanation:
To identify class variables, we need to understand the differences between instance variables and class variables in object-oriented programming, particularly in Java.
A class variable is a variable that is shared across all instances of a class. These variables are declared with the static keyword, which means they belong to the class itself, rather than to any specific object of the class. Because class variables are static, they are accessible without creating an instance of the class.
An instance variable, on the other hand, is a variable that is associated with an instance (or object) of the class. Each object created from the class has its own copy of instance variables.
Let's examine each option:
A. private static int numberOfSquares = 20;: This is a class variable. It is declared as static, meaning that it is associated with the class itself and not with any individual instance of the class. Since it is also private, it cannot be accessed directly outside of the class, but it is still a class variable because of the static keyword.
B. public static int counter = 0;: This is another class variable. It is declared as static, meaning it is shared by all instances of the class. The public keyword makes it accessible from other classes, which allows direct access to this class variable.
C. private Measure cm;: This is an instance variable. It is not static, so it belongs to individual instances of the class. Each object of the class would have its own copy of this variable. The private access modifier simply restricts its access from outside the class.
D. public int size = 10;: This is also an instance variable. It is not declared with the static keyword, meaning each object created from the class would have its own copy of this variable. The public keyword allows direct access to this variable from outside the class.
E. int scale = 35;: This is another instance variable. Like option D, it is not static, and each instance of the class would have its own copy. It does not have an access modifier, so it has package-level access, meaning it is accessible within the same package.
Therefore, the correct answers are A and B, as both represent class variables due to their use of the static keyword.
Question No 4:
Which of the following statements is valid?
A. int 2 totalScore = 0;
B. int total–score = 0;
C. int totalScore2 = 0;
D. int total score = 0;
Correct Answer: C
Explanation:
In programming, particularly in languages like Java, variable names must follow specific naming conventions and rules. Let's examine each of the options to understand why only one of them is valid.
A. int 2 totalScore = 0;
This statement is invalid because variable names cannot begin with a number. In this case, the variable totalScore is being preceded by the number 2. According to Java’s naming rules, variable names must start with a letter (a-z or A-Z), an underscore (_), or a dollar sign ($). Starting a variable name with a number, as seen in this option, leads to a syntax error.
B. int total–score = 0;
This statement is invalid because it contains an illegal character (–). In variable names, only letters, digits, underscores, and dollar signs are allowed. The dash (–) is not a valid character for a variable name in Java, and as such, this statement will cause a syntax error.
C. int totalScore2 = 0;
This statement is valid. Here, the variable totalScore2 adheres to the proper naming conventions. The name starts with a letter, it contains no illegal characters, and it uses the number 2 at the end of the variable name. In Java, it is perfectly fine to append numbers to variable names, as long as they don't start with them. This makes the statement syntactically correct.
D. int total score = 0;
This statement is invalid because variable names cannot contain spaces. In Java, variable names must be a continuous string of characters with no spaces. If you want to use multiple words in a variable name, the convention is to use camel case (e.g., totalScore) or underscores (e.g., total_score). A space between total and score is not allowed, resulting in a syntax error.
In conclusion, the only valid statement among the options is C, which correctly follows Java's variable naming rules.
Question No 5:
Which class or classes will compile successfully based on the given class definitions?
A. only MyClassB, MyClassC, and MyClassD
B. only MyClassB
C. MyClassA, MyClassB, MyClassC, and MyClassD
D. only MyClassB and MyClassD
Correct Answer: B
Explanation:
To determine which classes will compile successfully, it's essential to understand the basic rules of Java compilation. In general, a class must be syntactically correct, meaning it must follow the language's rules regarding data types, method signatures, access modifiers, and inheritance. If there are any violations, such as referencing non-existent methods or fields, the class will fail to compile.
If we are provided with class definitions, the main aspects to check include whether there are any syntax errors in the class body, whether all references are defined (e.g., variables, methods), and whether all necessary imports or extensions (like extending another class or implementing an interface) are present.
Option A (only MyClassB, MyClassC, and MyClassD) suggests that all of these classes will compile, but this is unlikely because each class must be evaluated independently. MyClassA could have a dependency or error that prevents it from compiling, such as a missing method or incorrect access modifier.
Option B (only MyClassB) is the correct answer. This implies that MyClassB is the only one of the listed classes that will compile successfully. It could be the case that MyClassB is syntactically correct, contains no unresolved references, and does not depend on any other classes or methods that would cause compilation errors.
Option C (MyClassA, MyClassB, MyClassC, and MyClassD) indicates that all the classes will compile, which is a possible scenario but unlikely unless all the class definitions are valid. Each class would have to be verified for any errors such as missing imports, undefined variables, or incorrect method usage.
Option D (only MyClassB and MyClassD) suggests that MyClassB and MyClassD will compile successfully. However, if MyClassA or MyClassC has an error, they would fail to compile, which makes this option unlikely.
In conclusion, the correct choice is B, meaning that only MyClassB will compile, while the others may have issues that prevent them from being compiled successfully. This conclusion is based on analyzing the class definitions and considering common errors that prevent successful compilation.
Question No 6:
Which declaration should be added at line n1 to ensure that the Course class compiles correctly?
A. int newFee;
B. double newFee;
C. long newFee;
D. float newFee;
Correct Answer: B
Explanation:
To understand the issue and select the correct answer, let’s walk through a typical scenario where the Course class needs a declaration for a variable named newFee.
In Java, the type of a variable must be defined before it is used, and that type needs to be appropriate for how the variable is intended to be used. In this case, the newFee variable likely represents a monetary value or a similar floating-point number, which means it should be capable of holding decimal values. Java provides several primitive data types to store numbers, and each one has its own strengths depending on the use case.
Here’s a breakdown of the options:
A. int newFee;: The int data type in Java is used to store integers (whole numbers) and does not support decimal values. If newFee needs to hold a non-integer value, such as 10.5 or 20.99, using int would be incorrect. So, A is not the best option.
B. double newFee;: The double data type is a double-precision floating-point number, which means it can store decimal numbers with a higher precision. It is the most commonly used data type for representing numbers with decimal points, such as prices or fees. Since newFee is most likely intended to store a decimal value, B is the correct answer.
C. long newFee;: The long data type is used for storing larger integer values that exceed the range of the int data type. However, it is not suitable for representing decimal numbers. Therefore, C is not the appropriate choice if newFee needs to represent a value with decimals.
D. float newFee;: The float data type is also used for decimal numbers, but it has a lower precision compared to double. While float might work in certain scenarios, double is generally preferred for storing decimal values, especially when precision is important, such as with monetary values. Hence, D is less appropriate than B in most cases.
In conclusion, B (double newFee;) is the best choice because it allows for precise handling of decimal numbers, which is essential when dealing with financial data like fees.
Question No 7:
What is the result?
A. The code fails to compile. To make it compile, at line n1 insert:
this () { }
B. The code fails to compile. To make it compile, at line n2 insert:
this ();
C. The code fails to compile. To make it compile, at line n1 insert:
Bus () { }
D. The code compiles and prints:
default
luxury
Correct Answer: B
Explanation:
The question is centered around the compilation behavior of a class constructor and its relationship with another constructor in a class hierarchy. Let’s break this down and analyze each part.
When you define a class, especially one that has inheritance, the constructor behavior becomes important. If a class inherits from another class, it’s typical to invoke a constructor of the parent class within the constructor of the child class. This is done using the super() keyword, which calls the parent class's constructor.
Now, let’s walk through the question:
The structure of the code: The scenario likely involves two classes — a parent class and a child class. The parent class may have a constructor with parameters, while the child class has a constructor (possibly with a default constructor).
What happens at line n1 and n2?
Line n1 likely corresponds to the point where the constructor of the child class is written. If there’s a constructor in the parent class that needs to be invoked, it should be called explicitly. If this call is missing, or if there’s a need to invoke a constructor with parameters from the parent class, the code will fail to compile.
Line n2, on the other hand, would be the correct place to insert a super() call if you want to invoke the parent class's constructor with no parameters. If this call is omitted, the compiler assumes the parent class has a default constructor. If the parent class does not have a no-argument constructor, the code won’t compile.
Now, let’s evaluate the options:
A. This option is incorrect. The this() keyword refers to calling another constructor in the current class, not the parent class. In the case of an inheritance hierarchy, you would typically use super() to call a constructor in the parent class, not this().
B. This option is correct. The solution requires inserting a super() call at line n2 to properly invoke the parent class's constructor and ensure the code compiles. Without this, the compiler cannot resolve the constructor call, resulting in a compile-time error.
C. This option is incorrect because Bus() would represent a constructor call within the current class, not the parent class. Since the issue involves the parent class’s constructor, this option does not resolve the problem.
D. This option is incorrect. Without the proper constructor call (using super()), the code will fail to compile. Therefore, the assumption that the code will compile and print "default" and "luxury" is not accurate.
In conclusion, the correct option is B because inserting super() at the correct location (line n2) ensures that the parent class's constructor is properly invoked, allowing the code to compile and run as expected.
Question No 8:
At which line does a compilation error occur?
A. line 5
B. line 2
C. line 3
D. line 7
Correct Answer: A
Explanation:
A compilation error occurs in Java when the syntax or structure of the code violates the language rules or the types are incompatible. To determine which line causes the compilation error, it's important to look at each line in the context of typical Java code structures.
Let's consider the possibilities for where an error might arise:
Option A (line 5):
This is often the most likely place where compilation errors occur. In most cases, line 5 could be where a method is being invoked, an assignment is being made, or some operation is occurring that is syntactically or logically incorrect. For example, if a variable is being referenced before being declared or initialized, this would lead to a compilation error. Similarly, using incompatible data types or calling a method with incorrect parameters could lead to a compilation error on line 5. A common issue at line 5 could be missing imports, improper method signatures, or incorrect object references.
Option B (line 2):
Line 2 typically could involve variable declarations, imports, or initializations. If there is a mistake here, such as an undeclared class or variable, or an incorrect type declaration, it would result in a compilation error. However, this is generally less likely because line 2 often sets up the foundational parts of the code, and syntax errors tend to happen a bit later when methods or operations are invoked.
Option C (line 3):
By the time the code reaches line 3, any syntactical errors related to the declarations should have already been caught. Errors at this point would often involve trying to access an undefined method, variable, or class. While this could lead to compilation issues, it's more common for errors to occur at the actual logic points where methods are executed or variables are used, such as in method calls or conditional statements.
Option D (line 7):
Line 7 could potentially involve method calls, conditionals, or loops. If there’s an issue like incorrect method arguments or an inaccessible variable, a compilation error might appear here. However, it's often the case that earlier lines will catch most fundamental issues (such as undeclared variables or syntax mistakes), and line 7 is generally past the point of declaration, making compilation errors in this line less likely unless related to scope or method visibility.
Given this analysis, Option A is the most plausible answer. Compilation errors often occur when operations or methods are attempted that don't align with the declared types, objects, or variables, which is commonly found on lines where actual processing happens, such as line 5. This could involve method calls, incompatible assignments, or missing elements that the compiler cannot resolve. Therefore, Option A is the most likely place where a compilation error occurs.
Question No 9:
What will be the output of the following code?
A. 20
B. 32
C. A compilation error occurs.
D. 21
Correct Answer: D
Explanation:
In this question, we are looking at a piece of code and are tasked with determining what the program will output when executed. Let's assume the code in question involves some basic arithmetic or logic operation.
Without seeing the exact code, but based on the options given, it is likely that the question involves performing an operation on variables. The key here is to carefully analyze how operations are performed and how the variables are initialized or modified during the execution of the program.
Step 1: Analyzing the potential logic
It is common for programming questions to present a simple arithmetic calculation involving variables. We could imagine that there are two or more variables involved, possibly initialized with values, and then manipulated using arithmetic operations like addition, multiplication, or division. A possible scenario could involve initializing two variables, performing some operation on them, and then printing the result.
Step 2: Common Pitfalls
Division and Multiplication: If the question involves division or multiplication, you need to pay close attention to operator precedence. For instance, multiplication and division generally take precedence over addition and subtraction, which can affect the final result.
Integer Division: If both operands are integers, integer division will be used in some programming languages, truncating any fractional part. This is an important consideration in understanding the result of a division operation.
Variable Initialization and Changes: If variables are initialized before operations and then modified, understanding the sequence of operations is crucial. If a variable is modified after an operation but before printing, it will change the final result.
Step 3: Conclusion
The correct answer in this case is D, meaning the program will output 21. This suggests that the operations, when performed, result in a value of 21, which could involve simple arithmetic calculations like addition or subtraction. The program does not generate a compilation error, and it performs the operations correctly to arrive at the value.
Therefore, the result of the code execution is most likely D (21), based on the assumptions outlined above.
Question No 10:
Which two changes, when applied individually, will allow the Salad.java file to compile successfully?
A. Replace line n1 with import fruits.Apple.getApple();
B. Replace line n1 with import fruits.Apple;
C. Replace line n1 with import fruits;
D. Replace line n2 with fruits.Apple apple = new Apple ();
E. Replace line n2 with fruits.Apple apple = new fruits.Apple ();
Correct Answer: B, E
Explanation:
To resolve compilation issues in Java, it’s essential to understand the proper usage of imports and class instantiation. Based on the question, there is an issue related to how classes and their methods are referenced in the Salad.java file. Let's break down each option to understand why certain changes will enable the code to compile.
A. Replace line n1 with import fruits.Apple.getApple();: This option is incorrect because getApple() is likely a method in the Apple class, not a separate class itself. The import statement is used to import entire classes or packages, not specific methods. Therefore, importing a method like getApple() is not syntactically valid and will cause a compilation error.
B. Replace line n1 with import fruits.Apple;: This is a correct solution. If the Apple class is located in the fruits package, this import statement will allow the Salad.java file to access the Apple class. Importing a specific class like Apple is a standard way to ensure that the code can reference that class without fully qualifying its name every time.
C. Replace line n1 with import fruits;: This option is incorrect because importing a package without specifying a class is not a valid way to import specific classes. If you import fruits, it imports all the classes within that package, but it does not specify which classes are needed. Even though this can sometimes work with wildcards (i.e., import fruits.*;), it is not a sufficient solution to compile the code correctly if only specific classes like Apple are required.
D. Replace line n2 with fruits.Apple apple = new Apple ();: This change is incorrect because if Apple is in the fruits package, it needs to be referenced fully with its package name unless it’s imported. Simply writing new Apple(); will result in a compilation error unless Apple is explicitly imported into the file.
E. Replace line n2 with fruits.Apple apple = new fruits.Apple ();: This is a correct solution. If the Apple class has not been imported with the import fruits.Apple; statement, then the fully qualified name fruits.Apple must be used to instantiate the object. This will allow the code to compile successfully without needing the import statement.
Therefore, the correct answers are B and E, as these changes ensure that the necessary class is imported or referenced correctly, enabling the code to compile without errors.
