java 完全平方数

要判断一个数是否是完全平方数，可以使用以下方法：

public class PerfectSquare {
    public static boolean isPerfectSquare(int num) {
        if (num < 0) {
            return false;
        }
        
        int left = 0;
        int right = num;
        
        while (left <= right) {
            long mid = left + (right - left) / 2;
            long square = mid * mid;
            
            if (square == num) {
                return true;
            } else if (square < num) {
                left = (int) mid + 1;
            } else {
                right = (int) mid - 1;
            }
        }
        
        return false;
    }
}