Conditional Constructs in Java — ICSE Class 10 Computer Applications

int marks = 41;
if (marks >= 33)
{
    System.out.println("Pass");
}
System.out.println("Result declared");

Output:

Pass
Result declared

“Result declared” hamesha chhapega — woh if block ke bahar hai. Sirf “Pass” conditional hai.

int a = 3;
if (a > 5);
    System.out.println("Inside");
System.out.println("Outside");

Output:

Inside
Outside

a = 3 hai, phir bhi “Inside” chhapa — kyunki semicolon ne if ka body khatam kar diya. Indentation compiler ke liye kuch matlab nahi rakhta.

int n = -7;
if (n % 2 == 0)
    System.out.println(n + " is even");
else
    System.out.println(n + " is odd");

Output:

-7 is odd

Dhyaan do: −7 % 2 ka answer −1 hai, 1 nahi. Isliye even test ke liye hamesha n % 2 == 0 likho — n % 2 == 1 negative numbers par fail ho jaata hai.

int year = 2024;
if ((year % 400 == 0) || (year % 4 == 0 && year % 100 != 0))
    System.out.println(year + " is a leap year");
else
    System.out.println(year + " is not a leap year");

Output:

2024 is a leap year

Yeh ek hi condition mein && aur || dono use karta hai — brackets lagana yahan optional nahi, zaroori hai, warna logic badal jaata hai.

int a = 17, b = 25;
int big = (a > b) ? a : b;
System.out.println("Bigger = " + big);

int m = 33;
System.out.println(m >= 33 ? "Pass" : "Fail");

Output:

Bigger = 25
Pass

33 >= 33 sach hai — boundary value par students aksar “Fail” likh dete hain. >= aur > ka farak dhyaan se padho.

int p = 4, q = 9;
String s = (p > q) ? "P" : (q % 2 == 0) ? "Q even" : "Q odd";
System.out.println(s);

Output:

Q odd

Pehla test (4 > 9) false, isliye colon ke baad wala poora hissa evaluate hua. 9 % 2 = 1, toh woh bhi false — answer “Q odd”. Ternary right se left group hota hai, isliye doosra ternary pehle wale ke else-part ke andar baith jaata hai.

int marks = 72;
char grade;
if (marks >= 90) grade = 'A';
else if (marks >= 75) grade = 'B';
else if (marks >= 60) grade = 'C';
else if (marks >= 40) grade = 'D';
else grade = 'E';
System.out.println("Marks = " + marks + ", Grade = " + grade);

Output:

Marks = 72, Grade = C

72 >= 90 → false. 72 >= 75 → false. 72 >= 60 → true, so grade = ‘C’ aur ladder wahin khatam. Neeche wali conditions check hi nahi hui.

double units = 310, bill;
if (units <= 100) bill = units * 3.0;
else if (units <= 300) bill = 100 * 3.0 + (units - 100) * 4.5;
else bill = 100 * 3.0 + 200 * 4.5 + (units - 300) * 6.0;
System.out.println("Units = " + units + ", Bill = " + bill);

Output:

Units = 310.0, Bill = 1260.0

300 + 900 + 60 = 1260. Aur dhyaan do — units double hai, isliye output 310.0 chhapa, 310 nahi. Slab programs mein yeh chhoti si baat marks kha jaati hai.

int n = 0;
if (n > 0) System.out.println("Positive");
else if (n < 0) System.out.println("Negative");
else System.out.println("Zero");

Output:

Zero

Zero ke liye alag condition likhne ki zaroorat nahi — else khud “na positive, na negative” ko pakad leta hai. Yeh ladder ka sabse saaf use hai.

int a = 12, b = 45, c = 45;
if (a > b)
{
    if (a > c) System.out.println("a is greatest");
    else System.out.println("c is greatest");
}
else
{
    if (b > c) System.out.println("b is greatest");
    else if (c > b) System.out.println("c is greatest");
    else System.out.println("b and c are equal and greatest");
}

Output:

b and c are equal and greatest

Bahar wali condition (12 > 45) false thi, isliye seedha else block mein gaye. Wahan b aur c barabar nikle. Zyadatar students tie ka case likhna bhool jaate hain — examiner exactly wahi test karta hai.

int a = 5, b = 5, c = 5;
if (a == b && b == c) System.out.println("Equilateral");
else if (a == b || b == c || a == c) System.out.println("Isosceles");
else System.out.println("Scalene");

Output:

Equilateral

Equilateral ka test pehle hona chahiye. Agar Isosceles wali line upar hoti, toh 5-5-5 bhi “Isosceles” chhapta — kyunki a == b sach hai.

int day = 3;
switch (day)
{
    case 1: System.out.println("Monday"); break;
    case 2: System.out.println("Tuesday"); break;
    case 3: System.out.println("Wednesday"); break;
    case 4: System.out.println("Thursday"); break;
    default: System.out.println("Some other day");
}
System.out.println("Done");

Output:

Wednesday
Done

Har case ke baad break laga hai, isliye sirf matching case chala aur switch se bahar aa gaye.

char ch = 'u';
switch (ch)
{
    case 'a':
    case 'e':
    case 'i':
    case 'o':
    case 'u':
        System.out.println(ch + " is a vowel");
        break;
    default:
        System.out.println(ch + " is a consonant");
}

Output:

u is a vowel

Yeh fall-through ka useful istemaal hai: paanchon vowel cases khaali hain, isliye control neeche behta hua ek hi statement tak pahunchta hai. Ek hi kaam, paanch entry points.

int day = 2;
switch (day)
{
    case 1: System.out.println("Monday");
    case 2: System.out.println("Tuesday");
    case 3: System.out.println("Wednesday");
    case 4: System.out.println("Thursday");
    default: System.out.println("Some other day");
}

Output:

Tuesday
Wednesday
Thursday
Some other day

case 2 par entry hui, aur phir sab kuch chal gaya — default tak. “Monday” nahi chhapa kyunki woh entry point se upar tha.

int k = 2;
switch (k + 1)
{
    case 2: System.out.print("Two ");
    case 3: System.out.print("Three ");
    case 4: System.out.print("Four "); break;
    case 5: System.out.print("Five ");
}
System.out.println("| over");

Output:

Three Four | over

k + 1 = 3, toh entry case 3 par. “Three ” chhapa, break nahi tha, isliye “Four ” bhi chhapa — aur wahan break mil gaya. “Five ” nahi chhapa.

int choice = 9;
double p = 8000, r = 5, t = 2;
switch (choice)
{
    case 1:
        System.out.println("Simple Interest = " + (p * r * t / 100));
        break;
    case 2:
        System.out.println("Amount = " + (p + p * r * t / 100));
        break;
    default:
        System.out.println("Invalid choice. Program terminated.");
        System.exit(0);
}
System.out.println("This line never runs for an invalid choice.");

Output:

Invalid choice. Program terminated.

Aakhri line chhapi hi nahi — System.exit(0) ne poora JVM band kar diya. break sirf switch se bahar nikalta hai; System.exit(0) program hi khatam kar deta hai. Yeh farak likhwana examiner ko bahut pasand hai.