fisr.java

public class fisr {                                                                
    public static void main(String[] args) {                                       
        System.out.println(invSqrt(Float.parseFloat(args[0])));                    
    }                                                                              
                                                                                   
    public static float invSqrt(float number) {                                    
        int i;                                                                     
        float x2, y;                                                               
        float threehalfs = 1.5F;                                                   
                                                                                   
        x2 = number * 0.5F;                                                        
        i = Float.floatToIntBits(number);                                          
        i = 0x5f3759df - (i >> 1);                                                 
        y = Float.intBitsToFloat(i);                                               
        y = y * (threehalfs - (x2* y * y));                                        
        return y;                                                                  
    }                                                                              
}