★★ Java の宿題ここで答えます Part 66 ★★

★★ Java の宿題ここで答えます Part 66 ★★ at TECH

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400:デフォルトの名無しさん
 08/11/17 04:02:09 
package net._2ch.pc11.tech._1221652206; 
import java.io.*; 
import java.math.*; 
public class Growth_rate { 
    public static void main(String args[]) throws IOException { 
        final BufferedReader reader =  
            new BufferedReader(new FileReader("tokyo23.txt")); 
        StringBuilder result = new StringBuilder(); 
        String line = reader.readLine(); 
        while (line != null) { 
            if (line.startsWith("131")) { 
                String[] data = line.split("\t"); 
                double population = Double.valueOf(data[2].trim()); 
                double growth = Double.valueOf(data[3].trim()); 
                BigDecimal percentage =  
                    new BigDecimal(growth / (population + growth) * 100); 
                percentage.setScale(2, RoundingMode.HALF_UP); 
                line = line + "\t" + String.format("%6.2f%%", percentage); 
            } 
            result.append(line); 
            result.append("\r\n"); 
            line = reader.readLine(); 
        } 
        reader.close(); 
        BufferedWriter writer =  
            new BufferedWriter(new FileWriter("tokyo23.txt")); 
        writer.write(result.toString()); 
        writer.close(); 
    } 
}

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