What will happen if the superclass method does not exist in the subclass while trying to override it?
- It will automatically create a new method in the subclass with the same name.
- It will lead to a compile-time error.
- It will result in a runtime error.
- It will use the superclass method without any issue.
In Java, when you try to override a method from a superclass in a subclass, the method in the superclass must exist; otherwise, it will lead to a compile-time error. Java enforces method signature matching during compile-time, so if the method doesn't exist in the superclass, the compiler will not find a method to override in the subclass, resulting in an error.
The ________ method of Throwable class can be used to retrieve the description of an exception.
- getDescription()
- getDescriptionText()
- getExceptionDescription()
- getMessage()
The getMessage() method of the Throwable class is used to retrieve the description or message associated with an exception. This message provides additional information about the exception, helping developers understand the cause of the error.
Which of the following classes is used to write characters to a file in Java?
- BufferedReader
- FileOutputStream
- FileWriter
- PrintWriter
The FileWriter class in Java is used to write characters to a file. It provides methods to write character data to a file in a character stream. FileOutputStream is used for writing binary data, PrintWriter is used for formatted text output, and BufferedReader is used for reading character data, not writing.
What happens if no constructor is provided in a Java class?
- The class cannot be instantiated, and objects of that class cannot be created.
- Java automatically provides a default no-argument constructor for the class.
- The class can only be instantiated by other classes in the same package.
- The class becomes a singleton by default.
a) is correct. If no constructor is provided in a Java class, Java automatically provides a default no-argument constructor. b) is a common misconception; Java only provides a default constructor if you haven't defined any constructors explicitly. c) and d) are incorrect statements.
The ________ method of the String class returns the index within this string of the first occurrence of the specified character, starting the search at the specified index.
- indexOf(char ch)
- indexOf(char ch, int fromIndex)
- lastIndexOf(char ch)
- lastIndexOf(char ch, int fromIndex)
The lastIndexOf(char ch, int fromIndex) method of the String class is used to find the index of the last occurrence of the specified character within the string, starting the search from the given index fromIndex. The other options are related to the indexOf method but don't perform the same task.
Which of the following is a primitive data type in Java?
- ArrayList
- Boolean
- String
- int
In Java, primitive data types are basic data types that store single values. int is one of the primitive data types and is used to store integer values. String, ArrayList, and Boolean are not primitive data types; they are reference data types or classes.
Imagine a situation where you need to insert a large dataset (for example, 10,000 rows) into a database using JDBC. How would you optimize this process to ensure that it is done efficiently and does not consume excessive resources?
- Disable database constraints temporarily during the insertion process.
- Execute individual INSERT statements in a loop for each row in the dataset.
- Increase the database transaction isolation level to SERIALIZABLE for the insertion operation.
- Use batch processing with prepared statements to insert multiple rows in a single database call.
Batch processing with prepared statements is the most efficient way to insert a large dataset into a database using JDBC. It reduces the overhead of multiple database calls by grouping multiple insertions into a single call. Executing individual INSERT statements in a loop is resource-intensive and not recommended for large datasets. Disabling database constraints can compromise data integrity. Increasing the transaction isolation level to SERIALIZABLE is not needed for a simple insertion operation.
The collect() method in the Stream API is a type of ________ operation.
- Intermediate
- Stateful
- Stateless
- Terminal
The collect() method is a terminal operation in the Stream API. It is used to accumulate the elements of a stream into a collection, such as a List or Set. Terminal operations are those that trigger the processing of the stream and produce a final result.
How can you access variables in the surrounding scope from a lambda expression?
- They are automatically accessible within the lambda.
- You can access them using the super keyword.
- You cannot access them.
- You need to pass them as parameters to the lambda expression.
To access variables from the surrounding scope within a lambda expression, you typically need to pass them as parameters to the lambda expression. This is known as "capturing" variables. Lambda expressions in Java can access effectively final local variables and instance variables. Attempting to access non-final variables can result in compilation errors.
The method ________ is used to execute SQL for DDL statements using JDBC.
- executeDDL()
- executeQuery()
- executeStatement()
- executeUpdate()
In JDBC, the method executeUpdate() is used to execute SQL statements that perform Data Definition Language (DDL) operations, such as creating, altering, or dropping database objects. It returns an integer representing the number of rows affected by the statement. executeQuery() is used for retrieving data, not DDL statements.