SCJP Flow Control (Loops, Branching, and Labeled Statements)

Question 1

What is the output of the following code?

int x = 5;
do {
    System.out.print(x + " ");
    x--;
} while (x > 5);

Accepted Answer

5

Answer

A do-while loop always executes its body at least once before checking the condition. Here x=5 is printed, then x becomes 4, and 4>5 is false so the loop exits. Output is '5'.

Question 2

Which of the following data types can be used as a switch expression in Java SE 6?

Accepted Answer

int

Answer

In Java SE 6, switch expressions are limited to byte, short, char, and int (and their wrappers, plus enum). String support was added in Java 7. long and boolean are never valid switch types.

Question 3

What does the following code print?

outer:
for (int i = 0; i < 3; i++) {
    for (int j = 0; j < 3; j++) {
        if (j == 1) break outer;
        System.out.print(i + "" + j + " ");
    }
}
System.out.print("done");

Accepted Answer

00 done

Answer

`break outer` terminates the entire outer for-loop when j==1. The only iteration that prints before that happens is i=0, j=0, producing '00'. Then j becomes 1, break outer fires, and execution jumps to the `System.out.print("done")` line.

Question 4

Which statement about the enhanced for-loop (for-each) is TRUE?

Accepted Answer

It requires the collection to implement java.lang.Iterable

Answer

The enhanced for-loop works with arrays and any object that implements java.lang.Iterable. It provides no index variable, cannot structurally modify the underlying collection, and Map does not implement Iterable so you must use keySet(), values(), or entrySet().

Question 5

What happens when the following code is compiled?

void test() {
    return;
    System.out.println("hello");
}

Accepted Answer

It fails to compile due to unreachable code

Answer

The Java compiler detects unreachable statements and reports a compile-time error. The `System.out.println` after an unconditional `return` can never execute, so the class will not compile.

SCJP - Sun Certified Java Programmer Practice Test

SCJP - Sun Certified Java Programmer Practice Test

SCJP Flow Control (Loops, Branching, and Labeled Statements)