พื้นฐานลูป for

แนวคิดการวนซ้ำแบบสามส่วน

for (int i = 0; i < 3; i = i + 1) {
  System.out.println("Loop " + i);
}

นับขึ้น

for (int i = 1; i <= 5; i = i + 1) {
  System.out.println(i);
}

นับถอยหลัง

for (int i = 5; i > 0; i = i - 1) {
  System.out.println(i);
}

สะสม

public class Main {
  public static void main(String[] args) {
    int sum = 0; // start with 0

    // Loop from 1 to 5 (inclusive)
    for (int i = 1; i <= 5; i = i + 1) {
      // Add current i to sum
      sum = sum + i;
    }

    // Print the result
    System.out.println("Sum = " + sum);
  }
}

หยุด/ดำเนินการต่อ

public class Main {
  public static void main(String[] args) {
    // Loop from 1 to 5
    for (int i = 1; i <= 5; i = i + 1) {
      if (i == 3) continue; // skip printing when i == 3
      if (i == 5) break;    // stop the loop completely when i == 5

      System.out.println(i); // print i if not skipped or stopped
    }
  }
}

สาธิตลูป

public class Main {
  public static void main(String[] args) {
    // Sum of even numbers 1..10
    int sumEven = 0;
    for (int i = 1; i <= 10; i = i + 1) {
      if (i % 2 == 0) sumEven = sumEven + i;
    }
    System.out.println("Sum of even 1..10 = " + sumEven);

    // Factorial of 5
    int fact = 1;
    for (int i = 1; i <= 5; i = i + 1) {
      fact = fact * i;
    }
    System.out.println("5! = " + fact);

    // Simple pattern (triangle)
    for (int row = 1; row <= 3; row = row + 1) {
      String line = "";
      for (int col = 1; col <= row; col = col + 1) {
        line = line + "*";
      }
      System.out.println(line);
    }
  }
}

ลูป 5..1

ทบทวนและถัดไป