Java quiz 1

What is garbage collection in Java?

• Code optimization technique

• Automatic memory management

• Data cleaning process

• Manual memory deallocation

Answer explanation

Garbage collection in Java refers to the automatic memory management process where the JVM automatically deallocates memory that is no longer needed by the program. This helps in preventing memory leaks and makes memory management easier for developers.

Which keyword is used to define a constant variable in Java?

• final

• immutable

• constant

• static

Answer explanation

The 'final' keyword is used to define a constant variable in Java. Once a variable is declared as final, its value cannot be changed throughout the program execution.

Which of the following is not a primitive data type in Java?

• String

• char

• boolean

• double

• int

Answer explanation

In Java, 'String' is not a primitive data type. It is a reference type that represents a sequence of characters. The primitive data types in Java are int, boolean, double, char, etc.

Which class is used to convert a primitive data type into an object in Java?

• Wrapper class

• Converter class

• Primitive class

• Object class

Answer explanation

Wrapper classes in Java, such as Integer, Double, Boolean, etc., are used to convert primitive data types into objects. This allows us to perform various operations on them using the methods provided by the wrapper classes.

How can you read user input from the console in Java?

• InputStreamReader class

• System.in

• BufferedReader class

• Scanner class

• Console class

Answer explanation

In Java, you can read user input from the console using various methods. The 'Scanner' class and the 'BufferedReader' class are commonly used for this purpose. 'System.in' represents the standard input stream, and 'InputStreamReader' is used to read character streams.

Which control statement is used to execute a block of code repeatedly as long as a condition is true?

• for loop

• switch statement

• while loop

• if statement

Answer explanation

The 'while' loop in Java is used to execute a block of code repeatedly as long as a condition is true. It checks the condition before each iteration and continues executing the code until the condition becomes false.

What is the output of the following code snippet? int x = 5;

int y = 10;

if (x > y) {

System.out.println("x is greater than y");

}

else if (x < y) {

System.out.println("x is less than y");

}

else {

System.out.println("x is equal to y");

}

Answer explanation

The output of the code snippet will be 'x is less than y'. Since the condition 'x < y' is true, the code inside the corresponding 'else if' block will be executed.

What is the purpose of the 'break' statement in Java?

• To exit the program

• To skip the current iteration of a loop

• To terminate a loop or switch statement

• To define a constant variable

Answer explanation

The 'break' statement in Java is used to terminate a loop or switch statement. When encountered, it immediately exits the loop or switch statement and continues with the next line of code after the loop or switch.

Which keyword is used to explicitly throw an exception in Java?

• catch

• finally

• throw

• try

Answer explanation

The 'throw' keyword in Java is used to explicitly throw an exception. It is followed by an instance of the exception class that you want to throw. This allows you to handle exceptional situations and provide appropriate error messages.

What is the result of the following expression? 5 + 3 * 2 - 1

• 12

• 6

• 8

• 10

Answer explanation

The result of the expression '5 + 3 2 - 1' is 10. In Java, multiplication and division have higher precedence than addition and subtraction. Therefore, the multiplication '3 2' is performed first, resulting in 6. Then, the addition and subtraction are performed from left to right.