4.1 For Loops

Similar to while loops, for loops run until a condition is false. Format of for loop below:

for (int i = 0; i < 5; i++) {
    System.out.println(i);
}

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Explanation

  • in the above for loop:
    • int i = 0 defines the iterating variable
    • i < 5 is the condition (once i < 5 is false, this loop breaks)
    • i++ is the incrementation of the iterating variable
    • System.out.println(i); is the body code that runs every time the loop iterates

For Each Loops:

  • Apart from iterating using an incrementing variable, you can also iterate through items in a list.

    Example of For Each loop below

int[] list = {1, 2, 3, 4, 5}; // any list
for (int item : list) { // for each item in the list, execute the body
    System.out.println(num); // body code
}

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Explanation:

  • in the above loop:
    • int item : list - this line is saying that for each item in the list, execute code below
    • System.out.println(num); - this line is the body code.

Fun For Loop Hack:

Create a program that iterates through a list of numbers (int_list = {0, 4, 51, 83, 92, 10, 123, 145}) using both a for loop and a for each loop, then split the numbers in the list into even/odd lists, and output them.

int[] int_list = {0, 4, 51, 83, 92, 10, 123, 145};

System.out.print("Even numbers: ");
for (int num : int_list) {
    if (num % 2 == 0) {
        System.out.print(num);
        System.out.print(" ");
    }
}

System.out.print("\nOdd numbers: ");
for (int i = 0; i < int_list.length; i++) {
    int num = int_list[i];
    if (num % 2 == 1) {
        System.out.print(num + " ");
    }
}

Even numbers: 0 4 92 10 
Odd numbers: 51 83 123 145