Loops for devs

src/main/java/com/amigoscode/_1_beginners/_1_thebasics/LoopExercises.java

@@ -8,36 +8,65 @@
  */
 public class LoopExercises {
 
-    public static void main(String[] args) {
+    static void main(String[] args) {
 
         // TODO: 1 - Write a for loop to print numbers 1 to 10
         // Hint: for (int i = 1; i <= 10; i++) { ... }
+        System.out.println("TODO 1");
+        for (int i = 1; i <= 10; i++) {
+            System.out.println(i);
+        }
 
 
         // TODO: 2 - Write a while loop to print numbers 10 down to 1 (countdown)
         // Hint: Declare a variable before the loop, use a condition, and decrement inside the loop.
-
+        System.out.println("TODO 2");
+        int num = 10;
+        while (num >= 1) {
+            System.out.println(num--);
+        }
 
         // TODO: 3 - Write a do-while loop that runs at least once
         // Print "This runs at least once!" inside the loop.
         // Use a condition that is false so the loop only runs once.
         // Hint: do { ... } while (condition);
+        System.out.println("TODO 3");
+        num = 20;
+        do {
+            System.out.println("This runs at least once!");
+            num = 5;
+        }while (num == 10);
 
 
         // TODO: 4 - Write a for loop to print only even numbers from 1 to 20
         // Hint: Use an if statement with the modulus operator (%) inside the loop,
         //       or increment by 2 starting from 2.
-
+        System.out.println("TODO 4");
+        for (int i = 1; i <= 20; i++) {
+            if (i % 2 == 0) {
+                System.out.println(i);
+            }
+        }
 
         // TODO: 5 - Write a for loop to calculate the factorial of 5 (5! = 120)
         // Declare a variable called factorial and initialize it to 1.
         // Multiply factorial by each number from 1 to 5.
         // Print the result.
+        System.out.println("TODO 5");
+        int factorial = 1;
+        for (int i = 1; i <= 5; i++) {
+            System.out.println(factorial *= i);
+        }
 
 
         // TODO: 6 - Use an enhanced for loop (for-each) to iterate over a String array
         // Declare a String array called fruits with at least 4 fruit names.
         // Use an enhanced for loop to print each fruit.
+        System.out.println("TODO 6");
+        String[] fruits = {"Apples", "Blueberries", "Blackberries", "Oranges"};
+        for (String fruit : fruits) {
+            System.out.println(fruit);
+        }
 
 
         // TODO: 7 - Write a nested for loop to print a 3x3 multiplication table
@@ -47,13 +76,30 @@ public static void main(String[] args) {
         //   3  6  9
         // Hint: Use System.out.print() for values on the same row,
         //       and System.out.println() to move to the next row.
+        System.out.println("TODO 7");
+        for (int i = 1; i <= 3; i++) {
+            for (int j = 1; j <= 3; j++) {
+                System.out.print(i * j + " ");
+            }
+                System.out.println(" ");
+        }
 
 
         // TODO: 8 - Use break and continue in a loop
         // Write a for loop from 1 to 10:
         //   - Use 'continue' to skip the number 5 (do not print it)
         //   - Use 'break' to stop the loop when you reach 8
         // Print each number that is not skipped.
-
+        System.out.println("TODO 8");
+        for (int i = 1; i <= 10; i++) {
+            if (i == 5) {
+                continue;
+            }
+            if (i == 8) {
+                System.out.println(i);
+                break;
+            }
+            System.out.println(i);
+        }
     }
 }

src/main/java/com/amigoscode/_1_beginners/_1_thebasics/Variables.java

@@ -11,27 +11,33 @@ public class Variables {
     public static void main(String[] args) {
 
         // TODO: 1 - Declare an int variable called age and assign it the value 25
-
+        int age = 25;
 
         // TODO: 2 - Declare a double variable called price and assign it the value 9.99
-
+        double price = 9.99;
 
         // TODO: 3 - Declare a boolean variable called isJavaFun and assign it the value true
-
+        boolean isJavaFun = true;
 
         // TODO: 4 - Declare a String variable called name and assign it your name
-
+        String name = "Jose";
 
         // TODO: 5 - Declare a char variable called grade and assign it the value 'A'
-
+        char grade = 'A';
 
         // TODO: 6 - Print all the variables above using System.out.println
         // Hint: You can print each variable on its own line, e.g.:
         //   System.out.println("Age: " + age);
-
+        System.out.println("Age: " + age);
+        System.out.println("Price: " + price);
+        System.out.println("isJavaFun: " + isJavaFun);
+        System.out.println("Name: " + name);
+        System.out.println("Grade: " + grade);
 
         // TODO: 7 - Declare a final (constant) variable called MAX_SCORE, set it to 100, and print it
         // Hint: Use the 'final' keyword before the type to make a constant
+        final int MAX_SCORE = 100;
+        System.out.println("MAX_SCORE: " + MAX_SCORE);
 
     }
 }

src/main/java/com/amigoscode/_2_developers/_1_loops/LoopExercises.java

@@ -21,6 +21,12 @@ public static void printMultiplicationTable(int n) {
         // TODO: 1 - Use nested for loops to print an n x n multiplication table.
         //  Outer loop iterates rows 1..n, inner loop iterates columns 1..n.
         //  Print each product followed by a tab, and a newline after each row.
+        for (int i = 1; i <= n; i++) {
+            for (int j = 1; j <= n; j++) {
+                System.out.print(i * j + "\t");
+            }
+            System.out.println(" ");
+        }
 
     }
 
@@ -35,7 +41,15 @@ public static int sumWithSkipAndStop(int n) {
         int sum = 0;
         // TODO: 2 - Loop from 1 to n. Use 'continue' to skip multiples of 3.
         //  Use 'break' to stop if sum exceeds 100. Add the current number to sum otherwise.
-
+        for (int i = 1; i <= n;i++) {
+            if (i%3 == 0) {
+                continue;
+            }
+            if (sum > 100) {
+                break;
+            }
+            sum+=i;
+        }
         return sum;
     }
 
@@ -53,7 +67,17 @@ public static String findInMatrix(int[][] matrix, int target) {
         //  Use nested loops to iterate through the matrix.
         //  When the target is found, set result to "Found at [row][col]" and
         //  use 'break search;' to exit both loops.
-
+        // [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
+        System.out.println("search: " + target);
+        for (int i = 0; i < matrix.length; i++) {
+            for (int j = 0; j < matrix.length; j++) {
+                if (target == matrix[i][j]) {
+                    result = "Found at [" + j +"][" + i + "]";
+                    System.out.println("break search;");
+                    break;
+                }
+            }
+        }
         return result;
     }
 
@@ -68,7 +92,9 @@ public static long factorial(int n) {
         long accumulator = 1;
         // TODO: 4 - Use a for loop from 1 to n (inclusive), multiplying accumulator
         //  by the loop variable each iteration. Return the result.
-
+        for (int i = 1; i <= n; i++) {
+            accumulator *= i;
+        }
         return accumulator;
     }
 
@@ -86,7 +112,16 @@ public static void printPyramid(int rows) {
         // TODO: 5 - Use nested loops to print a centered pyramid of stars.
         //  For each row i (0-based), print (rows - i - 1) spaces followed by (2 * i + 1) stars.
         //  Print a newline after each row.
-
+        // [[  *  ], [ *** ], [******], [*******], [*********]]
+        for (int i = 0; i < rows; i++) {
+            for (int j = 0; j < (rows - i - 1); j++) {
+                System.out.print(" ");
+            }
+            for (int j = 0; j < (2 * i + 1); j++) {
+                System.out.print("*");
+            }
+            System.out.println();
+        }
     }
 
     /**
@@ -100,7 +135,13 @@ public static String iterateBackwards(int[] arr) {
         StringBuilder sb = new StringBuilder();
         // TODO: 6 - Use a for loop starting from the last index down to 0.
         //  Append each element to sb. Add ", " between elements but not after the last one.
+        for (int i = arr.length; i >= 0; i--) {
+            sb.append(i);
+            if (i != 0) {
+                sb.append(", ");
+            }
 
+        }
         return sb.toString();
     }
 
@@ -118,7 +159,12 @@ public static int countUntilMatch(int target) {
         // TODO: 7 - Use while(true) to create an infinite loop.
         //  Each iteration: increment attempts, generate a random int between 1 and 100,
         //  and break if it matches the target.
-
+        while(true) {
+            attempts += 1;
+            if(target == random.nextInt(100) + 1) {
+                break;
+            }
+        }
         return attempts;
     }