Basic "for" Statements

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∟Basic "for" Statements

This section describes basic 'for' statement, which is a looping statement that executes the contained statement repeatedly with an initial logic, a looping condition, and an update logic.

"for" statements have 2 forms: basic "for" statements and enhanced "for" statements. Let's look at basic "for" statements in this tutorial first.

What Is Basic "for" Statement? - A basic "for" statement is a looping statement that executes the contained statement repeatedly with an initial logic, a looping condition, and an update logic.

Here is the syntax for a basic "for" statement.

for (initial_logic; looping_condition; update_logic) contained_statement

When a basic "for" statement is executed, the flow of control can be described as:

Step 1. Run "initial_logic".

Step 2. Evaluate "looping_condition". If result is "false", end the "for" statement.

Step 3. Run "contained_statement".

Step 4. Run "update_logic".

Step 5. Go back to Step 2.

The contained statement can be empty, a simple single statement, or a complex statement block. Here is a sample program that shows you how to use basic "for" statements:

/* BasicForStatementTest.java
 * Copyright (c) HerongYang.com. All Rights Reserved.
 */
class BasicForStatementTest {
   public static void main(String[] arg) {
      java.io.PrintStream out = System.out;
      int max = 20;
      int sum = 0;

      out.println("\"for\" statement with no contained statement:");
      for (int i = 0; i < max; sum += ++i);
      out.println("   Sum of 1 to 20: "+sum);
      sum = 0;

      out.println("\"for\" statement with a contained statement:");
      for (int i = 0; i < max; i++) sum += i;
      out.println("   Sum of 0 to 19: "+sum);

      out.println("\"for\" statement with a contained statement block:");
      for (int i = 3; i < max; i++) {
         boolean isPrime = true;
         for (int j = 2;  j <= i/2; j++) {
            isPrime = i%j > 0;
            if (!isPrime) break;
         }
         if (isPrime) out.println("   "+i+" is a prime number.");
      }
   }
}

If you compile and run the above program, you will see:

herong> java BasicForStatementTest.java

"for" statement with no contained statement:
   Sum of 1 to 20: 210

"for" statement with a contained statement:
   Sum of 0 to 19: 190

"for" statement with a contained statement block:
   3 is a prime number.
   5 is a prime number.
   7 is a prime number.
   11 is a prime number.
   13 is a prime number.
   17 is a prime number.
   19 is a prime number.