ICSE Class 10 Computer MCQ Solutions: Chapter 1 Java

Question 1: Same method signature in two methods

Question: What type of error occurs when two methods in the same class have the same method signature?

Correct answer: Syntax error.

Reason: Java must be able to identify which method is being called. A method signature depends on the method name and parameter list. If two methods in the same class have the same name and the same parameter list, the compiler cannot treat them as separate overloaded methods.

1. Same method name: yes.
2. Same parameter types in the same order: yes.
3. Duplicate method signature in the same class: invalid.

Final answer: Syntax error.

Question 2: Advantages of user-defined methods

Question: The advantages of user-defined methods are: (i) Reusability, (ii) Complexity, (iii) Modularity.

Correct answer: (i) and (iii).

Reason: A user-defined method lets a programmer write a task once and call it many times. This gives reusability. It also divides a large program into smaller named units, which gives modularity. Complexity is not an advantage; methods are used to reduce and manage complexity.

Final answer: Reusability and modularity.

Question 3: Parameter that receives values

Question: Parameters that receive values during a method call are called what?

Correct answer: Formal parameters.

Reason: In a method definition, the variables written inside the brackets are formal parameters. They receive values when the method is called. The values supplied in the call are actual parameters.

Example: In void display(int a), a is a formal parameter. In display(20), 20 is the actual parameter.

Final answer: Formal parameters.

Question 4: Valid method prototype

Question: Which is a valid method prototype: public int perform (int a; int b), public perform (int a, int b), public int perform (int a, int b), or public perform int (int a, int b)?

Correct answer: public int perform (int a, int b).

Reason: A Java method header follows this order: access modifier, return type, method name and parameter list. Parameters are separated by commas, not semicolons.

1. public is the access modifier.
2. int is the return type.
3. perform is the method name.
4. (int a, int b) is the parameter list.

Final answer: public int perform (int a, int b).

Question 5: Correct method invocation

Question: Which statement correctly invokes int display(int a, char ch)?

Correct answer: int m = display(45, 'A');

Reason: The method expects two arguments in order: first an int, then a char. The return type is int, so assigning the returned value to an integer variable is valid.

1. 45 is an integer.
2. 'A' is a character literal.
3. The order matches int a, char ch.

Final answer: int m = display(45, 'A');

Question 6: Convert RESPECT to lowercase

Question: Which Java statement converts the word RESPECT to lowercase?

Correct answer: "RESPECT".toLowerCase();

Reason: The method name is toLowerCase(). Java is case-sensitive, so tolowercase() is wrong. The method is called on the String object using the dot operator.

Final answer: "RESPECT".toLowerCase();

Question 7: Wrapper classes

Question: Which are wrapper classes: Boolean, boolean, character, Character?

Correct answer: Boolean and Character.

Reason: Primitive data types use lowercase names, such as boolean and char. Wrapper classes are class names and begin with uppercase letters, such as Boolean and Character.

Final answer: (i) and (iv).

Question 8: Wrapper class to primitive type

Question: Conversion of a wrapper class object to its corresponding primitive type is known as what?

Correct answer: Unboxing.

Reason: Unboxing extracts the primitive value from its wrapper object. For example, an Integer object can be converted to an int value. Autoboxing is the reverse process, where a primitive value is converted into its wrapper object.

Final answer: Unboxing.

Question 9: String method that returns only a positive integer

Question: Which String method results only in a positive integer: indexOf, lastIndexOf, compareTo, or length?

Correct answer expected in the MCQ: length().

Reason: The length() method returns the number of characters in a string. For a non-empty string, this value is positive. By contrast, indexOf() and lastIndexOf() return -1 when the searched character or substring is not found. The compareTo() method can return a negative value, zero or a positive value.

Teacher’s note: Strictly in Java, "".length() returns 0, so the safer statement is that length() returns a non-negative integer. In this ICSE MCQ, it is still the intended answer because the other methods can return negative values.

Final answer: length().

Question 10: Convert String to double

Question: Which method converts a String value to double?

Correct answer: Double.parseDouble(String).

Reason: Double is the wrapper class for the primitive type double. Its static method parseDouble() converts a numeric string into a primitive double.

Example: double x = Double.parseDouble("45.6"); stores the value 45.6 in x.

Final answer: Double.parseDouble(String).

Question 11: Error in System.out.println(x[x.length])

Question: What happens when System.out.println(x[x.length]); is executed?

Correct answer: Run time error.

Reason: If an array has length n, the valid index positions are from 0 to n - 1. The expression x.length gives n. Therefore, x[x.length] tries to access index n, which is outside the array.

1. Suppose x.length = 5.
2. Valid indices are 0, 1, 2, 3, 4.
3. x[5] is outside the array.

Final answer: Run time error, specifically an array index out of bounds error.

Question 12: Valid character array declaration

Question: Which declaration stores the gender of 80 employees as characters?

Correct answer: char gender[] = new char[80];

Reason: The variable must be an array of char values, and memory must be created for 80 elements. The square brackets show that gender is an array. The expression new char[80] creates the 80 storage locations.

Final answer: char gender[] = new char[80];

Question 13: Correct order to accept values into an array

Question: Arrange these statements to accept values into array a[]: a[i] = sc.nextInt();, int a[] = new int[10];, Scanner sc = new Scanner(System.in);, for(i = 0; i < 10; i++).

Correct answer: (ii), (iii), (iv), (i).

Reason: First create the array. Then create the Scanner object for input. Next start the loop so each array position is visited. Inside the loop, read one integer and store it in a[i].

1. int a[] = new int[10];
2. Scanner sc = new Scanner(System.in);
3. for(i = 0; i < 10; i++)
4. a[i] = sc.nextInt();

Teacher’s note: In a full Java program, i must already be declared, or the loop should be written as for(int i = 0; i < 10; i++).

Final answer: (ii), (iii), (iv), (i).

Question 14: Bubble sort inner loop operation

Question: In bubble sort, during each iteration of the inner loop, two adjacent elements are what?

Correct answer: Compared and swapped.

Reason: Bubble sort checks adjacent elements. If they are in the wrong order for the required sorting direction, the program swaps them. This repeated comparison and swapping moves the larger element towards the end in ascending order.

Final answer: (i) compared and (ii) swapped.

Question 15: Highest index in an array of 100 elements

Question: What is the highest index of an array with 100 elements?

Correct answer: 99.

Reason: Java array indexing starts at 0. Therefore, an array with 100 elements has positions 0 through 99.

Step check: Highest index = length − 1 = 100 - 1 = 99.

Final answer: 99.

Question 16: Dividing a program into simple methods

Question: An event manager divides work among subordinates. In a program, a task is divided into simple methods. Which feature is used?

Correct answer: Modularity.

Reason: Modularity means dividing a large task into smaller modules. In Java programs, methods act as modules because each method can handle one well-defined task.

Final answer: Modularity.