(模板)java文件读写与保留小数

import java.math.*;
import java.text.*;
import java.util.*;
import java.io.*;

public class Main {
	
	public static void main(String []args) throws IOException {
		
		Scanner cin = new Scanner(new File("trains.in"));  
        PrintWriter cout = new PrintWriter(new File("trains.out"));  
          
          
		double c = 3.155;
		BigDecimal t = BigDecimal.valueOf(3.155);
		java.text.DecimalFormat myFormat = new java.text.DecimalFormat("#.00");
		
		cout.println(myFormat.format(t));
		
        cin.close();  
        cout.close();
		
	}
	
}