JAVA小程序-判断闰年和求根公式

计算闰年，根据格里高利历，能被4整除且不能被100整除，或者能被4整除且能被400整除的年份为闰年

/******************************************************************************
 *  Compilation:  javac LeapYear.java
 *  Execution:    java LeapYear n
 *  
 *
 *  % java LeapYear 2004
 *  true
 *
 *  % java LeapYear 1900
 *  false
 *
 *  % java LeapYear 2000
 *  true
 *
 ******************************************************************************/

public class LeapYear { 
    public static void main(String[] args) { 
        int year = Integer.parseInt(args[0]);
        boolean isLeapYear;

        // divisible by 4
        isLeapYear = (year % 4 == 0);

        // divisible by 4 and not 100
        isLeapYear = isLeapYear && (year % 100 != 0);

        // divisible by 4 and not 100 unless divisible by 400
        isLeapYear = isLeapYear || (year % 400 == 0);

        System.out.println(isLeapYear);
    }
}

 

1元2次方程的求根公式，如果你忘了，自行google吧。

 

public class Quadratic {

　　public static void main(String[] args) {
　　// TODO Auto-generated method stub
　　double a = Double.parseDouble(args[0]);
　　double b = Double.parseDouble(args[1]);
　　double c = Double.parseDouble(args[2]);

　　double temp = 4.0 * a * c;
　　double discriminant = b*b - temp;

　　double sqroot = Math.sqrt(discriminant);

　　double root1 = (-b + sqroot) / (2.0 * a);
　　double root2 = (-b - sqroot) / (2.0 * a);

　　System.out.println(root1);
　　System.out.println(root2);
　　}

}