Control Statement in Java Worksheet

1. What is the core execution difference between a while loop and a do-while loop?

Answer:

  • while Loop (Entry-Controlled): Checks its condition before running the code block. If the initial condition is false, the code block inside will execute 0 times.

  • do-while Loop (Exit-Controlled): Runs the code block first, and then evaluates its condition at the bottom. The code block is guaranteed to execute at least 1 time, regardless of whether the initial condition is true or false.

 

2. What happens if you forget to add a break statement inside a switch case block?

Answer: Omitting break causes fall-through behavior. Java will execute the matching case code block, and then automatically continue executing all subsequent case blocks below it sequentially-ignoring their conditional expressions-until it hits a break or reaches the end of the switch statement.

 

3. How do break and continue alter the control flow inside a loop?

Answer:

  • break: Terminates the entire loop immediately. Control jumps out of the loop body to the next line of code below it.

  • continue: Skips only the remaining lines of code in the current iteration and jumps straight to the next loop evaluation step (updating counter variables).

 

4. What is an infinite loop? Write a minimal example using both for and while.

Answer: An infinite loop is a loop whose condition never evaluates to false, causing the loop body to run continuously until killed or system memory exhausts.

// Infinite while loop
while (true) { 
/* runs forever */ 
}

// Infinite for loop
for (;;) { 
/* runs forever */ 
}

5. What is a ternary operator, and how does it simplify an if-else statement?

Answer: The ternary operator (? :) is a shorthand syntax for simple if-else assignments. It evaluates a condition and yields one of two values.

// Standard if-else
int age = 19;
String status;
if (age >= 18) {
status = "Adult";
} else {
status = "Minor";
}

// Equivalent Ternary Operator
String status = (age >= 18) ? "Adult" : "Minor";


6. What data types are supported inside a Java switch expression?

Answer: Java Supports

  • Primitive types: byte, short, char, int

  • Wrapper classes: Byte, Short, Character, Integer

  • Enum types

  • String (supported starting in Java 7)

 

7. Predict the output of the following loop:

for (int i = 1; i <= 5; i++) {
if (i == 3) {
continue;
}
System.out.print(i + " ");
}

Answer: 1 2 4 5 

(Explanation: When i == 3, continue executes, skipping the System.out.print step for that iteration and jumping directly to i++).

 

8. Can an if condition evaluate an integer value directly, like if (1) in C/C++?

Answer: No. In Java, conditions inside if, while, or for control statements must evaluate strictly to a boolean type (true or false). Passing an integer like if (1) or if (0) triggers a compile-time error: Incompatible types: int cannot be converted to boolean.

 

9. What is a nested loop, and how many total iterations occur in the example below?

for (int i = 0; i < 3; i++) {
for (int j = 0; j < 4; j++) {
// Code block
}
}

Answer: A nested loop is a loop placed inside another loop. The inner loop executes completely for every single iteration of the outer loop.

  • Outer loop runs 3 times ($i = 0, 1, 2$).

  • Inner loop runs 4 times for each outer pass ($j = 0, 1, 2, 3$).

  • Total execution iterations = $3 \times 4 =$ 12 iterations.

 

10. Predict the output of this code snippet:

int count = 10;
do {
System.out.print(count + " ");
count++;
} while (count < 5);

Answer: 10
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