Keep two decimal places and take values upward

  Encounter an evaluation question , It roughly means that the result retains two decimal places , And take value upward . I think I have realized the function within the specified time , But the result is that you can't AC. Think about it later, probably because 1.200 This situation , It becomes 1.2, instead of 1.20.

  First of all, keep two decimal places and take values upward . Here is to solve a small financial problem ,ans It is the accurate result after calculation , There may be many decimal places after it , Because it's about keeping two decimal places , And whether to make progress 0.01 It is only related to the third digit after the decimal point , therefore , use (int)(ans * 1000) The operation of will remove the following decimal part , And turn the result into an integer , The single digits of this integer (ans1 % 10) That is to say ans The third digit after the decimal point of , Judge whether it is 0, If not for 0, The ten digits of an integer , That is, the second place after the decimal point of the original decimal +1, After processing , The third digit after the decimal point can be removed , Then change the integer back to decimal , Because what is required here is String type , use toString() The method is ok .

  static String calculate(int a, double i, int n) {
    	double ans = a * (i /1200) * Math.pow((1+i /1200),(n * 12)) / (Math.pow((1+i /1200),(n * 12))-1);
    	int ans1 = (int)(ans*1000);
    	if(ans1 % 10 != 0) 
    		ans1 = ans1 + 10;
    	ans1 = ans1 - ans1 % 10;
    	double res = ans1/1000.0;
    	String result = Double.toString(res);
    	return result;
    }

    Then talk about later thinking , about 1.200 This situation , It becomes 1.2, instead of 1.20.Java There is one DecimalFormat Class , It is very convenient to deal with the problem of number formatting .（ Reference source ： Click to open the link ）

import java.text.DecimalFormat;

public class Main1{   
	public static void main(String[]args){ 
		double pi=3.1415927;
		// Take an integer   
		System.out.println(new DecimalFormat("0").format(pi));//3  
		// Take one integer and two decimal places   
		System.out.println(new DecimalFormat("0.00").format(pi));//3.14  
		// Take two integers and three decimal places , The insufficient part of an integer is to 0 fill .  
		System.out.println(new DecimalFormat("00.000").format(pi));// 03.142  
		// Take all integral parts   
		System.out.println(new DecimalFormat("#").format(pi));//3  
		// Count as a percentage , And take two decimal places   
		System.out.println(new DecimalFormat("#.##%").format(pi));//314.16%  
		
		long c=299792458;// The speed of light   
		// It's shown as scientific counting , And take five decimal places   
		System.out.println(new DecimalFormat("#.#####E0").format(c));//2.99792E8  
		// Scientific counting that is displayed as two digit integers , And take four decimal places   
		System.out.println(new DecimalFormat("00.####E0").format(c));//29.9792E7  
	    // Every three digits are separated by commas .  
		System.out.println(new DecimalFormat(",###").format(c));//299,792,458  
		// Embedding formatting into text   
		System.out.println(new DecimalFormat(" The speed of light is per second ,### rice .").format(c));  
	}
}