ลูป for ซ้อนกันและรูปแบบข้อความ

แนวคิดลูปซ้อนกัน

สี่เหลี่ยมผืนผ้า 3x4

public class Main {
  public static void main(String[] args) {
    // Outer loop controls the number of rows (3 rows total)
    for (int r = 1; r <= 3; r = r + 1) {
      // Start with an empty string for each row
      String line = "";

      // Inner loop controls the number of columns (4 stars per row)
      for (int c = 1; c <= 4; c = c + 1) {
        // Add one star to the line in each iteration
        line = line + "*";
      }

      // Print the completed line of stars
      System.out.println(line);
    }
  }
}

สามเหลี่ยมมุมฉาก

public class Main {
  public static void main(String[] args) {
    // Outer loop controls the number of rows (from 1 up to 4)
    for (int r = 1; r <= 4; r = r + 1) {
      // Start with an empty string for each row
      String line = "";

      // Inner loop runs 'r' times, so stars increase with each row
      for (int c = 1; c <= r; c = c + 1) {
        // Add one star to the current line
        line = line + "*";
      }

      // Print the completed line of stars
      System.out.println(line);
    }
  }
}

จัดชิดขวา

public class Main {
  public static void main(String[] args) {
    int height = 4; // total number of rows for the triangle

    // Outer loop: controls the row number
    for (int r = 1; r <= height; r = r + 1) {
      String line = "";

      // First inner loop: add spaces so stars are right-aligned
      for (int s = 1; s <= (height - r); s = s + 1) {
        line = line + " ";
      }

      // Second inner loop: add stars according to current row
      for (int c = 1; c <= r; c = c + 1) {
        line = line + "*";
      }

      // Print the final line (spaces + stars)
      System.out.println(line);
    }
  }
}

ตาราง 1..3

public class Main {
  public static void main(String[] args) {
    // Outer loop controls the rows (1 to 3)
    for (int r = 1; r <= 3; r = r + 1) {
      String line = "";

      // Inner loop controls the columns (1 to 3)
      for (int c = 1; c <= 3; c = c + 1) {
        // Multiply row number (r) by column number (c)
        // Add the result plus a space to the line
        line = line + (r * c) + " ";
      }

      // Print the row after building it
      System.out.println(line);
    }
  }
}

สาธิตรูปแบบ

public class Main {
  public static void main(String[] args) {
    // Rectangle 3x4
    for (int r = 1; r <= 3; r = r + 1) {
      String line = "";
      for (int c = 1; c <= 4; c = c + 1) {
        line = line + "*";
      }
      System.out.println(line);
    }

    // Right triangle
    for (int r = 1; r <= 4; r = r + 1) {
      String line = "";
      for (int c = 1; c <= r; c = c + 1) {
        line = line + "*";
      }
      System.out.println(line);
    }

    // Right-aligned triangle
    int height = 4;
    for (int r = 1; r <= height; r = r + 1) {
      String line = "";
      for (int s = 1; s <= (height - r); s = s + 1) {
        line = line + " ";
      }
      for (int c = 1; c <= r; c = c + 1) {
        line = line + "*";
      }
      System.out.println(line);
    }
  }
}

สี่เหลี่ยมผืนผ้า 3x4

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