Java Conditional Statements: if, switch and ?: (ISC Class 11 Computer Science)

Understand Conditional Statements in Java: if, if-else-if, switch and the Ternary Operator

if (m >= 90) grade = 'A';
else if (m >= 70) grade = 'B';
else if (m >= 50) grade = 'C';
else grade = 'D';

switch (d) {
    case 1: System.out.print("Mon ");
    case 2: System.out.print("Tue "); break;
    case 3: System.out.print("Wed ");
    case 4: System.out.print("Thu "); break;
    default: System.out.print("Off");
}

Conditional Statements in Java: if, if-else-if, switch and the Ternary Operator: key facts

Ternary

result = condition ? valueIfTrue : valueIfFalse | Both values must suit the type

Replaces a simple if-else.

Leap year

(y % 4 == 0 && y % 100 != 0) || y % 400 == 0 | 2000 true, 2100 false

Gregorian rule.

switch flow

• •Jump to matching case
• •Continue until break
• •default if no match

Fall-through.

How to answer Conditional Statements in Java: if, if-else-if, switch and the Ternary Operator questions

1. 1Substitute the values into the condition.
2. 2Take the first true branch in an if-else-if chain.
3. 3For switch, jump to the matching case and continue until a break.
4. 4Write the output exactly, with spaces.

Conditional Statements in Java: if, if-else-if, switch and the Ternary Operator in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Tricks to remember Conditional Statements in Java: if, if-else-if, switch and the Ternary Operator

Short memory aids. Say each one aloud once, then use it on a question the same day.

• First true wins

  Else-if stops at the first true condition.

  Use it when: if-else-if.

• Break to stop

  Without break, switch falls through.

  Use it when: switch.

• Equals twice

  Compare with ==, assign with =.

  Use it when: Conditions.

Conditional Statements in Java: if, if-else-if, switch and the Ternary Operator: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Where students lose marks in Conditional Statements in Java: if, if-else-if, switch and the Ternary Operator

The slips examiners see most often, and what to write instead.

• ✗Mistake: Using = in a condition

  Typing slip.

  Wrong working

  if (x = 5)

  Right working

  if (x == 5)

  ✓Do this: == compares.

  Usually costs: 1-2 marks.

• ✗Mistake: Forgetting break in switch

  Assuming it stops.

  Wrong working

  Only Wed printed for 3

  Right working

  Wed Thu

  ✓Do this: Check for break.

  Usually costs: 2 marks.

• ✗Mistake: Pairing else with the outer if

  Looks aligned.

  Wrong working

  Y for (3, 10)

  Right working

  Nothing

  ✓Do this: Else joins the nearest if.

  Usually costs: 2 marks.

Practice questions on Conditional Statements in Java: if, if-else-if, switch and the Ternary Operator

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQBoard level

   The output of int x = 5; String r = (x > 3) ? "yes" : "no"; is:
   (a) yes (b) no (c) true (d) error

   Hint

   5 > 3.

   Answer

   (a) yes

2. Q2 · 2 marks · Short answerBoard level

   Write the output for k = 3 and then for k = 1: switch (k) { case 1: System.out.print("A"); case 2: System.out.print("B"); break; case 3: System.out.print("C"); case 4: System.out.print("D"); default: System.out.print("E"); } (2 marks)

   Hint

   Look for the breaks.

   Answer

   k = 3: CDE (falls through case 4 into default). k = 1: AB (stops at the break).

3. Q3 · 4 marks · Short answerHarder board level

   Write a Java fragment to print "Positive", "Negative" or "Zero" for an integer n, using if-else-if, and a one-line ternary version for "Even" or "Odd". Give the outputs for n = -4 and n = 7. (4 marks)

   Hint

   n % 2 == 0.

   Answer

   if (n > 0) ... else if (n < 0) ... else ... ; String t = (n % 2 == 0) ? "Even" : "Odd"; For n = -4: Negative, Even. For n = 7: Positive, Odd.

4. Q4 · 5 marks · Long answerHarder board level

   A shop gives a discount: 20% on bills above Rs 5,000, 10% on bills above Rs 2,000 up to Rs 5,000, and none otherwise. Write the if-else-if ladder and the payable amount for bills of Rs 6,000, Rs 2,500 and Rs 1,800. (5 marks)

   Hint

   Test the largest bill first.

   Answer

   if (b > 5000) pay = b * 0.80; else if (b > 2000) pay = b * 0.90; else pay = b; 6,000 gives 4,800; 2,500 gives 2,250; 1,800 gives 1,800.

5. Q5 · 3 marks · Short answerHOTS / competency

   A student writes: int a = 0; if (a != 0 & 10 / a > 2) ... and another writes if (a != 0 && 10 / a > 2) ... Explain which one fails when a is 0 and why. (3 marks)

   Hint

   Short-circuit.

   Answer

   The first uses the non-short-circuit & so 10 / a is evaluated and throws ArithmeticException; the second uses && and stops at a != 0 being false, so the division is never evaluated.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.Condition type in if?Show answer

   boolean.

2. 2.switch falls through without?Show answer

   break.

3. 3.Ternary form?Show answer

   condition ? a : b.

4. 4.Else belongs to?Show answer

   The nearest unmatched if.

5. 5.&& is?Show answer

   Short-circuit AND.

Conditional Statements in Java: if, if-else-if, switch and the Ternary Operator: frequently asked questions