find the sum of the even-valued terms

Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:

1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...

By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.

public class FibonacciSequence {

	public static void main(String args[]){
		int sum = 0;
		int a = 1;
		int b = 2;
		int c = 3;
		/**
		 * 求偶数之和
		 * 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, ...
		 * a, b, c
		 *    a, b, c
		 *       a, b, c
		 *          a, b, c
		 * */
		while (b < 4000000){
			sum += b;			
			a = b + c;
			b = a + c;
			c = a + b;
		}
		System.out.println(sum);
	}
}