Navigating Conditional Asteroids: Java Loops and Decisions

Introduction to the Lesson

Welcome to our exploration of how to combine Java loop structures with conditional statements. By merging these elements together, your loops will be supercharged, enabling them to perform versatile actions based on different conditions.

Reviewing Java Loop Structures

Before charging forward, it's essential to revisit the foundation: loops. Within the vast cosmos of Java, we've navigated two primary types of loops: the for and while loops. A for loop iterates a predetermined number of times, much like a reliable spaceship following a set route: Java for (int i = 0; i < 5; i++) { // Iterates five times System.out.println(i); // Prints 0 to 4} The while loop, on the other hand, repeats actions until a specified condition turns false: Java int i = 0; while (i < 5) { // Condition for the loop to continue System.out.println(i); // Prints 0 to 4 i++; // Increment the counter}

Reviewing Java Conditional Statements

Let's now revisit the if-else construct, which is Java's machinery for making decisions. Java int asteroidsDistance = 10; if (asteroidsDistance > 15) { // If this condition is true System.out.println("Navigate through the asteroids."); // This line executes} else {System.out.println("Steer clear of the asteroids."); // Else, this line executes} The if-else statement enables the spaceship to decide whether to navigate through the asteroids based on their distance.

Combining Loops and Conditional Statements

Next, consider how the for loop integrates with an if-else statement: Java for (int i = 0; i < 6; i++) { // Our loop will iterate 6 times if (i % 2 == 0) { // If the number is divisible by 2 (Even) System.out.println(i + " is even."); // It'll print "X is even."} else { // If not divisible by 2 (Odd) System.out.println(i + " is odd."); // It'll print "X is odd."}} // Prints: // 0 is even. // 1 is odd. // 2 is even. // 3 is odd. // 4 is even. // 5 is odd. In a similar fashion, an if-else statement can be applied within a while loop: Java int i = 0; while (i < 7) { // Our loop will iterate 7 times if (i % 3 == 0) { // If the number is divisible by 3 System.out.println(i + " is divisible by 3."); // It'll print "X is divisible by 3."} else { // If not divisible by 3 System.out.println(i + " is not divisible by 3."); // It'll print "X is not divisible by 3."} i++; // Increments the counter.} // Prints: // 0 is divisible by 3. // 1 is not divisible by 3. // 2 is not divisible by 3. // 3 is divisible by 3. // 4 is not divisible by 3. // 5 is not divisible by 3. // 6 is divisible by 3.

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Real-life Examples

Picture this scenario: you've prepared a shopping list (an array). As you proceed through the market (akin to the for loop), you check items (the if condition) off your list. If discounts are available, you purchase the luxury goods; if not, you buy them only if they're essential.

Java

String[] shoppingList = {"Potatoes", "Tomatoes", "Luxury Martian Rice"};
boolean discount = true;

for (String item : shoppingList) { // Iterating over the shopping list
    // If a discount is available on a luxury item, it will be purchased.
    // Else, if it's an essential item, it will be purchased.
    // Otherwise, the luxury item will be skipped.
    if (item.equals("Luxury Martian Rice") && discount) {
        System.out.println("Buy " + item + " with discount.");
    } else if (!item.equals("Luxury Martian Rice")) {
        System.out.println("Buy essential " + item);
    } else {
        System.out.println("No discount. Skip " + item);
    }
}

String[] shoppingList = {"Potatoes", "Tomatoes", "Luxury Martian Rice"};
boolean discount = true;

for (String item : shoppingList) { // Iterating over the shopping list
    // If a discount is available on a luxury item, it will be purchased.
    // Else, if it's an essential item, it will be purchased.
    // Otherwise, the luxury item will be skipped.
    if (item.equals("Luxury Martian Rice") && discount) {
        System.out.println("Buy " + item + " with discount.");
    } else if (!item.equals("Luxury Martian Rice")) {
        System.out.println("Buy essential " + item);
    } else {
        System.out.println("No discount. Skip " + item);
    }
}

In another setting, consider a space game. As long as you have life points (represented by a while loop), your points increase if you hit an alien (an if condition)!