Logic Control Exercises

To reinforce flow control concepts, consider the following implementtaions for common algorithmic tasks.

Parity Check

Determining whether an integer is even or odd using modular arithmetic:

int value = 7;
if (value % 2 == 0) {
    System.out.println("Even");
} else {
    System.out.println("Odd");
}

Rendering a Diamond Pattern

Constructing a symmetrical shape using nested loops requires managing spaces and symbols relative to the row index:

int height = 5;
int midpoint = height / 2 + 1;

// Upper section
for (int row = 1; row <= midpoint; row++) {
    for (int spaces = 0; spaces < midpoint - row; spaces++) System.out.print(" ");
    for (int stars = 0; stars < 2 * row - 1; stars++) System.out.print("*");
    System.out.println();
}

// Lower section
for (int row = midpoint - 1; row >= 1; row--) {
    for (int spaces = 0; spaces < midpoint - row; spaces++) System.out.print(" ");
    for (int stars = 0; stars < 2 * row - 1; stars++) System.out.print("*");
    System.out.println();
}

Series Summation

Calculating the sum of factorials (1 + 1/2! + 1/3! + ... + 1/20!) efficiently using a single loop:

double totalSum = 0;
double currentFactorial = 1;
for (int i = 1; i <= 20; i++) {
    currentFactorial *= i;
    totalSum += 1.0 / currentFactorial;
}
System.out.println(totalSum);

Working with Strings

In Java, String is a class rather than a primitive type. While you can instantiate strings using various constructors, literal assignment is the standard practice.

Initialization Methods

// Using character arrays
char[] data = {'j', 'a', 'v', 'a'};
String str1 = new String(data);

// Sub-segment extraction
String str2 = new String(data, 0, 2); // Result: "ja"

// Literal assignment (preferred for memory efficiency via the String Pool)
String str3 = "Java Programming";

String Concatenation

Java supports simple concatenation using the + operator. When mixing non-string types with strings, Java automatically converts the primitive values into their string representations. Operator precedence is critical when performing arithmetic within a concatanation statement:

int pages = 50;
double hours = 2.5;

// Implicit conversion
System.out.println("Read " + pages + " pages in " + hours + " hours.");

// Explicit grouping for arithmetic
System.out.println("Total work units: " + (pages + hours));