Learn APEX with Real Code Examples

public class Counter {
    public Integer count = 0;
    public Boolean isDark = false;

    public void updateUI() {
        System.debug('Counter: ' + count);
        System.debug('Theme: ' + (isDark ? 'Dark' : 'Light'));
    }

    public void increment() { count++; updateUI(); }
    public void decrement() { count--; updateUI(); }
    public void reset() { count = 0; updateUI(); }
    public void toggleTheme() { isDark = !isDark; updateUI(); }
}

// Simulate actions
Counter c = new Counter();
c.updateUI();
c.increment();
c.increment();
c.toggleTheme();
c.decrement();
c.reset();

Demonstrates a simple counter with theme toggling using Apex classes and console output (system debug).

public class AddProgram {
    public Integer a = 5;
    public Integer b = 3;
    public Integer sum;

    public void calculate() {
        sum = a + b;
        System.debug('Sum: ' + sum);
    }
}

AddProgram ap = new AddProgram();
ap.calculate();

Adds two numbers and prints the result using System.debug.

public class FactorialProgram {
    public Integer n = 5;
    public Integer fact = 1;

    public void calculate() {
        for(Integer i = 1; i <= n; i++) {
        fact *= i;
        }
        System.debug('Factorial: ' + fact);
    }
}

FactorialProgram fp = new FactorialProgram();
fp.calculate();

Calculates factorial of a number using a loop.

public class FibonacciProgram {
    public void generate() {
        List<Integer> fib = new List<Integer>{0,1};
        for(Integer i=2;i<10;i++) {
        fib.add(fib[i-1]+fib[i-2]);
        }
        System.debug('Fibonacci: ' + fib);
    }
}

FibonacciProgram fp = new FibonacciProgram();
fp.generate();

Generates first 10 Fibonacci numbers using Apex lists.

public class MaxProgram {
    public Integer a = 7;
    public Integer b = 10;

    public void findMax() {
        Integer max = (a > b) ? a : b;
        System.debug('Max: ' + max);
    }
}

MaxProgram mp = new MaxProgram();
mp.findMax();

Finds the maximum of two numbers.

public class ArraySum {
    public void sumArray() {
        List<Integer> nums = new List<Integer>{1,2,3,4,5};
        Integer sum = 0;
        for(Integer n : nums) { sum += n; }
        System.debug('Sum: ' + sum);
    }
}

ArraySum as = new ArraySum();
as.sumArray();

Sums elements of an integer list.

public class EvenNumbers {
    public void filter() {
        List<Integer> nums = new List<Integer>{1,2,3,4,5,6,7,8,9,10};
        for(Integer n : nums) {
        if(n % 2 == 0) System.debug(n);
        }
    }
}

EvenNumbers en = new EvenNumbers();
en.filter();

Displays even numbers from a list.

public class ConcatStrings {
    public void concat() {
        String str1 = 'HELLO';
        String str2 = 'WORLD';
        String result = str1 + str2;
        System.debug('Concatenated: ' + result);
    }
}

ConcatStrings cs = new ConcatStrings();
cs.concat();

Concatenates two strings and prints the result.

public class LoopCounter {
    public void run() {
        Integer count = 1;
        while(count <= 5) {
        System.debug('Counter: ' + count);
        count++;
        }
    }
}

LoopCounter lc = new LoopCounter();
lc.run();

Counts from 1 to 5 using a loop with debug output.

public class ConditionalIncrement {
    public void run() {
        Integer count = 3;
        if(count < 5) count++;
        System.debug('Counter: ' + count);
    }
}

ConditionalIncrement ci = new ConditionalIncrement();
ci.run();

Increment counter only if below 5.