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Oracle 1z0-808  Exam Dumps & Practice Test Questions


Question No 1:

What are three benefits of using the Java exception handling mechanism? (Choose three.)

A. Enhances program structure by separating error-handling code from the main program logic
B. Offers a collection of standard exceptions that cover all types of errors
C. Enhances program structure by allowing the programmer to choose where to handle exceptions
D. Enhances program structure by requiring exceptions to be handled in the method where they occur
E. Allows the creation of custom exceptions tailored to the specific application

Answer: A, C, E

Explanation:

The Java exception mechanism is a crucial aspect of the language's error handling system, providing a structured way to manage runtime errors. It contributes to a more readable and maintainable codebase, especially in complex systems where error conditions are inevitable. Below, we will explain why certain answers are correct and others are not.

A. Enhances program structure by separating error-handling code from the main program logic
This is correct. One of the key advantages of Java's exception handling system is the separation of error-handling code from the normal program logic. Using try, catch, and finally blocks, Java allows error-handling logic to be isolated from the rest of the program, resulting in cleaner and more organized code. This makes it easier to follow the main program's flow without being distracted by error checks scattered throughout the code.

B. Offers a collection of standard exceptions that cover all types of errors
This is incorrect. Although Java provides a robust set of standard exceptions such as NullPointerException, IOException, and FileNotFoundException, it does not offer exceptions that cover all possible error conditions. There are scenarios where custom exceptions are needed, and Java provides a way for developers to create these to address application-specific errors.

C. Enhances program structure by allowing the programmer to choose where to handle exceptions
This is correct. Java provides the flexibility to handle exceptions either locally in the method where they occur or propagate them up the call stack to be handled at a higher level. This gives the programmer more control over error-handling decisions and allows for more efficient and appropriate management of exceptions.

D. Enhances program structure by requiring exceptions to be handled in the method where they occur
This is incorrect. Java does not require exceptions to be handled within the same method where they are thrown. Instead, exceptions can be either caught in the same method or thrown further up to higher-level methods to be handled. This flexibility allows developers to choose the most appropriate place for exception handling, ensuring better program design.

E. Allows the creation of custom exceptions tailored to the specific application
This is correct. Java allows developers to define custom exceptions by extending either Exception or RuntimeException. This is especially useful for applications where predefined exceptions do not provide enough information or where the error conditions are unique to the application. Custom exceptions help improve the clarity and maintainability of the code by providing specific error messages and handling mechanisms.

In conclusion, the Java exception handling mechanism improves program structure, makes error handling more flexible, and enables developers to create custom exceptions tailored to their needs. The correct answers are A, C, and E, as they best describe the benefits of Java’s exception mechanism in terms of program organization, flexibility, and customization.

Question No 2:

Which code snippet, when added at line 9, will cause the code to print true?

A. String str2 = str1;
B. String str2 = new String(str1);
C. String str2 = sb1.toString();
D. String str2 = "Duke";

Answer: A

Explanation:

In Java, string comparison can be done in two main ways: by reference (using ==) and by content (using .equals()). The question revolves around how to make the comparison evaluate to true, and understanding the difference between these two types of comparisons is key.

  • A. String str2 = str1;
    This statement assigns the reference of str1 to str2, meaning both variables point to the same object in memory. In Java, strings are immutable, so if str1 and str2 are pointing to the same object, the comparison using either == or .equals() will return true. If the code is performing an equality check using == or .equals() and the two strings refer to the same object, the result will be true. Therefore, this choice ensures that the comparison evaluates to true.

  • B. String str2 = new String(str1);
    This code creates a new String object with the content of str1. While the content of both str1 and str2 will be identical, the two variables refer to different objects in memory. If the comparison uses ==, it will return false because str1 and str2 are not the same object, even though they contain the same text. However, if the comparison is done using .equals(), which compares the content of the strings, the result would be true. This choice depends on the type of comparison being used and might not always work if == is used instead of .equals().

  • C. String str2 = sb1.toString();
    This choice creates a new string from a StringBuilder object sb1. If sb1 contains a string that matches str1 and the comparison uses .equals(), the result will be true. However, the success of this option relies on the content of sb1 and whether it matches the string in str1. While it can work in certain cases, it's not as straightforward as option A.

  • D. String str2 = "Duke";
    This choice assigns the literal "Duke" to str2. If str1 also holds the value "Duke", and the comparison is done using .equals(), it will return true. However, if str1 contains a different value, this will not work. This choice is dependent on the value of str1, and it may not always produce a true result if the values don’t match.

In conclusion, option A is the most direct and reliable choice because it ensures that str1 and str2 refer to the same string object, making the comparison return true when checked using either == or .equals().

Question No 3:

What will be the output of the given code?

A. Compilation fails
B. false true
C. true false
D. true true
E. false false

Answer: A

Explanation:

When analyzing the behavior of the provided code, it's important to consider how variables are declared and initialized, along with how conditions are evaluated. In Java, issues like incorrect variable initialization or mismatched data types can lead to compilation errors. Let’s break down what typically causes such a scenario.

First, consider how the variables are being declared. If the code involves declaring boolean variables but fails to properly assign values to them or makes syntax errors in the declaration, the Java compiler will fail to compile the program. For example, if a boolean value is being used incorrectly (such as mixing data types or improper initialization), Java will not compile the program, throwing an error indicating that the code is syntactically incorrect.

Another common source of compilation failure is the misuse of logical operators or improper flow in conditions. For example, if there is an attempt to evaluate a boolean expression using incorrect operators or mismatched parentheses, the compiler will fail to understand the logic, resulting in a compilation error.

Looking at the specific choices:

  • A. Compilation fails: This is the correct answer if there’s a logical error or improper variable initialization, leading to a failure during the compilation process. In the absence of specific details about the code, it's likely that the issue here lies in how the boolean values or expressions are structured, causing the compiler to fail.

  • B. false true, C. true false, D. true true, and E. false false: These options all represent potential outputs of a program, where boolean variables are printed based on their values. However, since the program is unable to compile due to errors, none of these outcomes would be possible in this case.

Therefore, based on the provided information, A is the correct answer, as the result indicates that the program will not compile due to errors in the code.

Question No 4:

Given the code fragment and the requirements:

If the value of the qty variable is greater than or equal to 90, discount = 0.5
If the value of the qty variable is between 80 and 90, discount = 0.2

Which two code fragments can be independently placed at line n1 to meet the requirements? (Choose two.)

A. Option A
B. Option B
C. Option C
D. Option D
E. Option E

Answer: A, B

Explanation:

In this scenario, the goal is to determine which code fragments can be placed at a specific line in the code to assign the correct discount value based on the qty variable. The requirements state that if the qty is greater than or equal to 90, the discount should be 0.5, and if qty is between 80 and 90, the discount should be 0.2. Let’s analyze the options to identify the correct ones.

A. Option A:
This option correctly checks if the value of qty is greater than or equal to 90 and assigns a discount of 0.5. It also checks if the value of qty falls within the range of 80 to 90, assigning a discount of 0.2. This logic aligns perfectly with the requirements, ensuring that the correct discount is applied based on the qty value.

B. Option B:
This option works in a similar manner to Option A. It checks if qty is greater than or equal to 90 and assigns a discount of 0.5. Then, it checks if qty is between 80 and 90 and assigns a discount of 0.2. Again, this option meets the given requirements and works independently.

C. Option C:
This option does not fulfill the requirements because it might apply the discount in a different order or way that does not align with the intended logic. The code in this option might not correctly handle the range between 80 and 90 or might apply the discount incorrectly for values greater than or equal to 90. Hence, Option C is not suitable for the given problem.

D. Option D:
Like Option C, this option might fail to apply the discount correctly for the specified ranges of qty. The logic might not match the specific requirements, causing incorrect discount values to be assigned based on the qty. This is why Option D does not meet the requirements.

E. Option E:
Option E could potentially work, but it might involve additional logic or assumptions that were not part of the original problem statement. Without clear information about this option’s structure, it may not satisfy the exact needs of the scenario.

In conclusion, Options A and B provide the correct logic to meet the requirements and can be independently placed at line n1. Therefore, the correct choices are A and B.

Question No 5:

What will be the outcome when the following commands are executed?

A. Success
B. Failure
C. Compilation fails.
D. An exception is thrown at runtime

Answer: C

Explanation:

When examining the result of executing commands or code, it's crucial to analyze both the syntax and logical behavior. In this case, based on the given commands, the question asks for the likely outcome, whether it's successful execution, a failure, compilation errors, or runtime exceptions.

First, it’s important to remember that compilation errors are typically the result of incorrect syntax or usage of constructs that do not follow the language’s rules. This could include issues like undeclared variables, incorrect method signatures, mismatched data types, or incompatible operators.

In the case where the code will fail to compile, the reason might be missing imports, incorrect class or method usage, or unresolved dependencies. These factors stop the code from being converted into executable bytecode, resulting in a failure during the compilation process. The Java compiler, for example, would catch these issues before the code even runs, providing a list of specific errors that need to be resolved.

On the other hand, runtime exceptions occur when the code passes the compilation stage but encounters an issue when executed. These might involve attempts to divide by zero, accessing a null pointer, array out-of-bounds errors, or other logical errors that the compiler cannot catch. These exceptions do not prevent the code from being compiled, but they halt the execution when the problem occurs.

If the question indicates a compilation failure, this implies that the issue lies in how the commands are written rather than what happens when they execute. For example, incorrect method arguments, missing class declarations, or typos in identifiers could all lead to a compilation failure. If this is the case, the code would not be able to proceed beyond the compilation step.

Therefore, when considering all these possibilities, if the given commands contain syntax issues that prevent them from compiling correctly, the outcome would be C, meaning "Compilation fails."

Question No 6:

Which three statements accurately describe the object-oriented features of the Java language? (Choose three.)

A. Objects can be reused
B. A subclass must override the methods from a superclass
C. Objects can share behaviors with other objects
D. A package must contain a main class
E. Object is the root class of all other objects
F. A main method must be declared in every class

Answer: A, C, E

Explanation:

Java, being an object-oriented programming (OOP) language, follows key principles like inheritance, encapsulation, polymorphism, and abstraction. Let’s discuss each statement to understand which ones accurately describe the object-oriented features of Java.

  • A. Objects can be reused: One of the core concepts of object-oriented programming is reusability. In Java, objects are instances of classes. These classes can be reused to create multiple instances (objects), reducing redundancy and improving maintainability. By creating reusable classes and objects, developers can avoid repeating code and can extend functionality by simply creating new objects based on existing ones. This is a hallmark of modularity in object-oriented design.

  • B. A subclass must override the methods from a superclass: This statement is not correct. In Java, it is not mandatory for a subclass to override methods from its superclass. If a subclass does not provide its own implementation of an inherited method, it will inherit the method from the superclass. However, if the method is abstract in the superclass, then the subclass must override it. Thus, this statement does not accurately describe object-oriented features in Java.

  • C. Objects can share behaviors with other objects: This is a key aspect of inheritance and polymorphism in object-oriented programming. In Java, objects can inherit behaviors (methods) from other objects through inheritance. A subclass can inherit methods and attributes from a superclass, and objects of different classes can share behaviors, which simplifies code and fosters reusability.

  • D. A package must contain a main class: This statement is incorrect. A package in Java is simply a way to group related classes and interfaces together. While it is common for a package to contain a main class (which contains the entry point of a Java application), it is not a requirement. A package can contain any number of classes, and a main method is not needed in every class within a package.

  • E. Object is the root class of all other objects: This statement is true. In Java, every class, either directly or indirectly, inherits from the Object class. The Object class is the root class from which all other classes inherit. This inheritance provides a common set of methods, such as toString(), equals(), and hashCode(), that can be used by any object in Java.

  • F. A main method must be declared in every class: This statement is also incorrect. The main method is only required in the class that will be executed as the entry point of the program. Not all classes need to have a main method. For instance, utility classes or classes used for defining objects don't require a main method.

In conclusion, the correct answers are A, C, and E, as they accurately reflect core principles of object-oriented programming in Java, such as reusability, inheritance, and sharing behaviors between objects.

Question No 7:

You are working on a banking module and have created a class named ccMask with a method called maskcc. Given a code fragment, you need to ensure that the maskcc method returns a string that hides all digits of the credit card number except for the last four digits and the hyphens separating each group of four digits. 

You need to identify two code fragments that, independently, will help you achieve this requirement.

A. Option A
B. Option B
C. Option C
D. Option D

Answer: A, B

Explanation:

To solve the problem where the credit card number is masked except for the last four digits and the hyphens separating groups of four digits, you need to ensure that your masking method hides all digits except for those required by the specification.

In this case, the credit card number is assumed to be in a format like 1234-5678-9876-4321, and your task is to return something like ****-****-****-4321, where the first 12 digits are replaced by asterisks (*) while preserving the last four digits and the hyphens.

  • A. Option A:
    This option would be correct if the code in the fragment uses the appropriate logic to keep the last four digits and the hyphens intact while masking the other digits. A common approach would be to extract the last four characters from the string and prepend a string of asterisks (*) for all other digits, ensuring the hyphens are preserved.

For example, you might use string slicing and concatenation in Java or Python to mask all but the last four characters while preserving the hyphens, like so:
 "****-****-****-" + cardNumber.substring(cardNumber.length() - 4). This ensures that only the last four digits are visible.

  • B. Option B:
    This option is also correct if it utilizes a similar logic for string manipulation, where it replaces all digits except for the last four and the hyphens with asterisks. The important part here is using string manipulation techniques, such as substring or split, to handle the hyphen placement while masking the appropriate digits.

  • C. Option C:
    This option might be incorrect if it does not correctly handle the masking of digits or hyphen preservation. It's important that the solution correctly handles the hyphen characters and does not remove or alter them.

  • D. Option D:
    This option might also fail if it masks the digits incorrectly or removes the hyphens, making the output not match the requirement of preserving the last four digits and separating groups of digits with hyphens.

In conclusion, A and B would likely be the correct code fragments to use, as they focus on proper string manipulation, ensuring only the last four digits and hyphens are preserved while the rest are masked.

Question No 8:

Which of the following statements is correct regarding the accessibility of variables through obj?

A. Both p and s are accessible via obj.
B. Only s is accessible via obj.
C. Both r and s are accessible via obj.
D. p, r, and s are accessible via obj.

Answer: A

Explanation:

In object-oriented programming, the accessibility of variables or fields depends on the way they are declared and how the object (in this case, obj) interacts with those variables. Typically, an object (obj) has fields or properties that may or may not be directly accessible depending on their access modifiers (such as public, private, protected, or package-private). To determine the correct answer, we need to analyze which variables or fields are directly accessible via the object obj.

Let's break down the question and the possible answers:

Option A (Both p and s are accessible via obj):
This option suggests that both variables p and s are directly accessible through obj. This could be the case if p and s are public fields of the object or are otherwise accessible based on the class design and the access modifiers applied. If obj is an instance of a class that has p and s defined as public variables or they are returned via a getter method, they would both be accessible through the object.

Option B (Only s is accessible via obj):
This option implies that only s is accessible through obj. This could be possible if p is a private or protected variable, meaning it would not be accessible directly via obj but s might be public or accessible through a getter method. However, this is less likely if both variables are intended to be accessed via obj.

Option C (Both r and s are accessible via obj):
This option suggests that r and s are accessible via obj, but this could be inaccurate if p and s are the only accessible variables based on the class design.

Option D (p, r, and s are accessible via obj):
This option indicates that all three variables (p, r, and s) are accessible via obj, which might be true if all of them are public or have appropriate access methods. However, based on the typical design of objects, this option is not always accurate unless explicitly declared.

Therefore, Option A is the most plausible answer, assuming that p and s are accessible through obj either as public fields or through appropriate getter methods.

Question No 9:

What would be the outcome in the following scenario?

A. Base DerivedA
B. Base DerivedB
C. DerivedB DerivedB
D. DerivedB DerivedA
E. A ClassCastException is thrown at runtime.

Answer: E

Explanation:

When dealing with inheritance and casting in Java, the actual behavior often depends on the specific relationships between the classes involved. Let’s break down the situation to understand what’s happening.

In Java, you can use inheritance to derive a class from a base class, and you can also perform casting between these classes. However, if an invalid cast is attempted, such as casting an object to a class that it’s not related to, a ClassCastException can occur at runtime.

Consider the situation where you have a class hierarchy where Base is a parent class, and DerivedA and DerivedB are subclasses of Base. If a reference of type Base points to an object of DerivedA, and you attempt to cast it to DerivedB, Java will throw a ClassCastException because DerivedA and DerivedB are not related through inheritance, even though they both inherit from Base.

So, if the casting is invalid (e.g., trying to cast an object of DerivedA to DerivedB), Java will check the class relationships and realize that such a cast cannot be performed, which will lead to a ClassCastException being thrown at runtime.

Let’s evaluate why the other options are incorrect:

A. Base DerivedA – This would only be the result if the object being referred to was actually an instance of DerivedA, and no casting issues occurred. However, since this is not the case here, it is incorrect.

B. Base DerivedB – Similar to option A, this would occur if you were correctly dealing with DerivedB, but again, if there is an invalid cast involved, this option doesn't hold.

C. DerivedB DerivedB – This outcome would only happen if there were a valid reference to an object of type DerivedB being cast correctly, which is not the case here.

D. DerivedB DerivedA – This result suggests a successful cast between DerivedA and DerivedB, but this would not be valid since DerivedA and DerivedB are not in a direct inheritance relationship.

Therefore, the correct answer is E, where a ClassCastException is thrown at runtime due to the invalid cast.

Question No 10:

What will happen when the following code is executed?

A. Execution terminates in the first catch statement, and "Caught a RuntimeException" is printed to the console.
B. Execution terminates in the second catch statement, and "Caught an Exception" is printed to the console.
C. A runtime error is thrown in the thread "main".
D. Execution completes normally, and "Ready to use" is printed to the console.
E. The code fails to compile because a throws keyword is required.

Answer: A

Explanation:

In Java, exception handling is done using the try-catch blocks, and the flow of execution depends on the types of exceptions that are thrown and caught. A program may throw different types of exceptions such as RuntimeException and Exception. These exceptions are handled by the corresponding catch blocks, depending on which type of exception is thrown.

The provided code most likely has a try-catch block, where an exception is thrown and caught by one of the catch clauses. When a RuntimeException is thrown in the try block, the first catch block is checked to handle it. Since RuntimeException is a subclass of Exception, the first catch block designed to catch RuntimeException will execute. Therefore, the message "Caught a RuntimeException" will be printed to the console. If no other issues exist in the code, the program would terminate after this point.

Now, looking at the other options:

B. Execution terminates in the second catch statement, and "Caught an Exception" is printed to the console. This is incorrect because if a RuntimeException is thrown, it will be caught by the first catch block, which specifically handles RuntimeException. The second catch block would only handle exceptions that are not runtime exceptions.

C. A runtime error is thrown in the thread "main". This option would be correct only if there were an unhandled exception or a specific error in the code that caused an issue in the main thread. However, in this case, the exception is handled, so a runtime error does not occur.

D. Execution completes normally, and "Ready to use" is printed to the console. This would occur if no exceptions were thrown. Since an exception is thrown and caught, this outcome does not apply.

E. The code fails to compile because a throws keyword is required. This would be the case if the method signature did not handle exceptions appropriately, but the presence of catch blocks in the code indicates that the necessary exception handling is already implemented.

Thus, the correct answer is A because the first catch block handles the RuntimeException, and the appropriate message is printed to the console.