ICSE Computer Applications worksheets, one for every chapter, answers below.

Write on paper, not in BlueJ, because the board paper is handwritten. Mark strictly: an output missing a .0 or a space is wrong. Then write the reason beside each lost mark; after eight sheets that list shows which chapter needs another week.

Worksheet 3: User-defined methods

1. Which pair can NOT both appear in one class? (a) int f(int) and int f(double) (b) int f(int) and double f(int) (c) void f() and void f(int) (d) int f(int, char) and int f(char, int) [1]
2. Give the output: static int twice(int x) { x = x * 2; return x; } and in main int n = 6; int m = twice(n); System.out.println(n + " " + m); [2]
3. State whether pure or impure: (i) int square(int a) that returns a * a; (ii) void addBonus(int[] marks) that adds 5 to every element. [2]
4. Write the prototype of a public method isPrime that takes an int and returns true or false. [2]
5. Write a class with two overloaded methods named check: check(int n) prints whether n is even or odd; check(String s, char ch) prints how many times ch occurs in s. Call both from main. [15]

public class Check {
    void check(int n) {
        if (n % 2 == 0) System.out.println(n + " is even");
        else System.out.println(n + " is odd");
    }
    void check(String s, char ch) {
        int c = 0;
        for (int i = 0; i < s.length(); i++)
            if (s.charAt(i) == ch) c++;
        System.out.println(ch + " occurs " + c + " times");
    }
    public static void main(String[] args) {
        Check obj = new Check();
        obj.check(15);
        obj.check("banana", 'a');
    }
}

// Output: 15 is odd
//         a occurs 3 times

Three more overloading programs in board format are on user-defined methods and overloading.

Worksheet 4: Constructors

1. The return type of a constructor is (a) void (b) int (c) the class type (d) it has none [1]
2. Find the error and correct it: class Box { int side; void Box(int s) { side = s; } } used as Box b = new Box(4); [2]
3. Give the output: class Counter has Counter() { count = 10; } and Counter(int c) { count = c * 2; }; main makes new Counter() as x and new Counter(7) as y, then prints x.count + y.count. [2]
4. State two differences between a constructor and a method. [2]
5. Define a class Student with name and marks, a parameterised constructor, a method grade() that returns 'A' for 80 and above, 'B' for 60 to 79 and 'C' below 60, and display() that prints all three. Test it with Kabir, 72. [15]

public class Student {
    String name;
    int marks;
    Student(String n, int m) {
        name = n;
        marks = m;
    }
    char grade() {
        if (marks >= 80) return 'A';
        else if (marks >= 60) return 'B';
        else return 'C';
    }
    void display() {
        System.out.println(name + " " + marks + " " + grade());
    }
    public static void main(String[] args) {
        Student s = new Student("Kabir", 72);
        s.display();
    }
}

// Output: Kabir 72 B

Worksheet 7: Arrays

1. Binary search needs the array to be (a) sorted (b) of even length (c) of int type only (d) two dimensional [1]
2. Give the output: int[] v = {4, 9, 2, 7}; int s = 0; for (int i = 0; i < v.length; i += 2) s += v[i]; System.out.println(s + v[v.length - 1]); [2]
3. For int[][] g = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}}; give the sum of the left diagonal, g[2][0], and g.length * g[0].length. [2]
4. Show the array after the first pass of bubble sort, ascending, on {5, 1, 4, 2}. [2]
5. Write a program to input ten integers into an array, sort them in descending order by selection sort, and print them. [15]

import java.util.Scanner;
public class SortDesc {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int[] a = new int[10];
        System.out.println("Enter 10 integers:");
        for (int i = 0; i < 10; i++) a[i] = sc.nextInt();
        for (int i = 0; i < 9; i++) {
            int big = i;                     // index of largest so far
            for (int j = i + 1; j < 10; j++)
                if (a[j] > a[big]) big = j;
            int t = a[i]; a[i] = a[big]; a[big] = t;
        }
        for (int i = 0; i < 10; i++) System.out.print(a[i] + " ");
        System.out.println();
    }
}

// Input: 12 5 89 -3 40 40 7 0 66 21
// Output: 89 66 40 40 21 12 7 5 0 -3

Bubble sort, linear search and binary search are written in full on sorting and searching programs.

Worksheet 8: String handling

1. "COMPUTER".substring(3, 6) returns (a) "PUTE" (b) "PUT" (c) "MPU" (d) "MPUT" [1]
2. Give the output: String s = "Board Exam"; System.out.println(s.indexOf('a') + " " + s.lastIndexOf('a') + " " + s.charAt(s.length() - 1)); [2]
3. Give the output: System.out.println("apple".compareTo("apricot")); [2]
4. Give the output: String t = "java"; t.toUpperCase(); System.out.println(t + t.replace('a', 'o')); [2]
5. Write a program to input a sentence and print its longest word and that word's length. If two words tie, print the first. [15]

import java.util.Scanner;
public class Longest {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter a sentence: ");
        String s = sc.nextLine().trim() + " ";   // space marks the last word's end
        String word = "", longest = "";
        for (int i = 0; i < s.length(); i++) {
            char ch = s.charAt(i);
            if (ch != ' ') word += ch;
            else {
                if (word.length() > longest.length()) longest = word;
                word = "";
            }
        }
        System.out.println(longest + " " + longest.length());
    }
}

// Input: Practice makes the programs easier
// Output: Practice 8

Palindromes, vowel counts and word rearranging are on ICSE Class 10 string programs.