Questions and Answers
Which statement is true regarding the int data type in Java?
What is the output of the following code? int x = 10; int y = ++x + x++; System.out.println(y);
What will the following code produce? double d = 9.78; int i = (int) d;
How does a reference variable in Java function?
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What happens if you invoke nextInt() on a Scanner object and the next token isn't an integer?
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Which escape sequence in Java denotes a newline?
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What is the output of the following code? String str = 'Hello World'; System.out.println(str.substring(0, 5));
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Which method from the Math class is used to determine the absolute value of a number?
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What is the default value of the int data type in Java?
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What will be the value of y after executing the code 'int y = 10 + ++x;' if x is initially set to 5?
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What is the effect of casting a double to an int in Java?
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Which of the following correctly describes the purpose of a reference variable?
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What exception is thrown when nextInt() encounters a non-integer input?
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Which escape sequence is used for a tab character in Java?
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What will be the output of the code 'System.out.println(str.substring(6, 11));' with str initialized to 'Hello World'?
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Which method would you use to round a floating-point number up to the nearest integer in Java?
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What value will the variable 'num' contain after executing the following code: Random rand = new Random(); int num = rand.nextInt(10); System.out.println(num);?
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What will be the final value of 'sum' after executing this loop: int sum = 0; for (int i = 1; i <= 5; i++) { sum += i; }?
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If x = 2 and y = 3, which output will occur from the following code snippet? 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"); }
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Which expression correctly uses a logical operator to check if 'a' is greater than 'b' and 'c' is less than 'd'?
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What will the following switch statement print if 'day' is set to 3: switch(day) { case 1: System.out.println("Sunday"); break; case 2: System.out.println("Monday"); break; case 3: System.out.println("Tuesday"); break; default: System.out.println("Invalid day"); }?
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How do you correctly declare an array of integers in Java?
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What is the output of the following code: int[] arr = {1, 2, 3, 4, 5}; System.out.println(arr);?
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Which method is used to find the length of an array in Java?
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Which of the following statements correctly creates an instance of the Book class?
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How do you check if two objects obj1 and obj2 of the same class are equal in Java?
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Study Notes
Primitive Data Types
- The
intdata type is a 32-bit signed integer with a default value of 0.
Operators
- The expression involving
++xandx++in the codeint y = ++x + x++;evaluates to 22. - Precedence of operators affects the evaluation order in expressions.
Casting and Parsing
- When casting a
doublevalue of 9.78 toint, the resulting value will be 9 due to truncation of the decimal part.
References (Variables)
- A reference variable in Java stores the memory address of an object rather than its actual value.
Scanner Class and its Methods
- Calling
nextInt()on a Scanner object when input is not an integer will throw anInputMismatchException.
Escape Sequences
- The escape sequence
\nis used in Java to represent a newline character.
String Class and its Methods
- The output of
System.out.println(str.substring(0, 5));for the string "Hello World" will be "Hello".
Math Class and its Methods
- To compute the absolute value of a number, use the method
Math.abs().
Random Class and its Methods
- The
nextInt(10)method from the Random class generates a random integer between 0 and 9.
Loops, Accumulators, Incrementors
- Value of
sumafter a loop iteration depends on the logic and initialization of the loop (not fully provided).
Primitive Data Types, Rules, & Hierarchy
-
intis a 32-bit signed integer with a default value of 0. - Cannot store decimal values; only whole numbers are allowed.
ASCII, Arithmetic & Increment/Decrement Operators, Precedence
- Given code output:
int x = 10; int y = ++x + x++;results inybeing 22 due to pre-increment and post-increment behavior.
Casting and Parsing
- Casting a
double d = 9.78tointresults inibeing 9, as it truncates the decimal part.
References (Variables)
- A reference variable in Java holds the memory address of an object rather than the object itself.
Scanner Class and its Methods
- Calling
nextInt()on a Scanner object when input is not an integer will throw anInputMismatchException.
Escape Sequences
- The escape sequence for a newline in Java is
\n.
String Class and its Methods
- Code
String str = "Hello World"; System.out.println(str.substring(0, 5));outputs "Hello".
Math Class and its Methods
- To find the absolute value of a number, use the method
Math.abs().
Random Class and its Methods
-
Random rand = new Random(); int num = rand.nextInt(10);prints a random number between 0 and 9.
Loops, Accumulators, Incrementors
- After completing the loop where
sumaccumulates values, the finalsumwill depend on the logic within the loop.
Conditional Statements
- Comparing values using
ifstatements establishes relationships. For example,xbeing less thanyprints "x is less than y".
Logical Operators
- The expression
a > b && c < dcorrectly checks ifais greater thanbandcis less thand.
Switch Statements
- For
int day = 3;, the switch statement outputs "Tuesday" as it matches the case for day 3.
Arrays: Declaring, Traversing, Populating
- Declare an array of integers using
int[] arr = new int[n];wherenis the size.
Output of Arrays
- Printing an array directly (e.g.,
System.out.println(arr);) does not return individual elements but rather the object reference.
Length of Arrays
- Use
arr.lengthto determine the size of an array in Java.
Objects: Declaration, Scope, Fields, References, Equality
- Create an instance of a class using
Book myBook = new Book();.
Variable Scope
- A variable declared within a method has a method-level scope.
Object Equality
- To compare objects for equality, use
obj1.equals(obj2).
Object Methods: Signature Lines, Constructors, Accessors, Mutators
- A correct constructor signature is
public Car() {}. - An accessor method example is
public String getName()for retrieving a property.
Mutator Methods
- The method
setAge(int age)is categorized as a mutator, as it modifies the state of the object.
Static and Non-Static Methods
- Static methods can only access static variables, while non-static methods can access instance variables.
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Description
Test your knowledge on primitive data types, rules, and operator precedence in Java. Answer questions related to the int data type and its properties, as well as increment and decrement operations. This quiz will help you solidify your understanding of fundamental Java concepts.
