Java從控制台讀入數據的幾種方法

這裡記錄Java中從控制台讀入信息的幾種方式，已備後查！

(1)JDK 1.4(JDK 1.5和JDK 1.6也都兼容這種方法)

 
public class TestConsole1 {  
    public static void main(String[] args) {  
        String str = readDataFromConsole("Please input string：);  
        System.out.println("The information from console： + str);  
    }  
  
    /** 
     * Use InputStreamReader and System.in to read data from console 
     *  
     * @param prompt 
     *             
     * @return input string 
     */  
    private static String readDataFromConsole(String prompt) {  
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));  
        String str = null;  
        try {  
            System.out.print(prompt);  
            str = br.readLine();  
  
        } catch (IOException e) {  
            e.printStackTrace();  
        }  
        return str;  
    }  
}  

(2)JDK 1.5（利用Scanner進行讀取）

 
public class TestConsole2 {  
    public static void main(String[] args) {  
        String str = readDataFromConsole("Please input string:");  
        System.out.println("The information from console:" + str);  
    }  
  
    /** 
     * Use  java.util.Scanner to read data from console 
     *  
     * @param prompt 
     *  
     * @return input string 
     */  
    private static String readDataFromConsole(String prompt) {  
        Scanner scanner = new Scanner(System.in);  
        System.out.print(prompt);  
        return scanner.nextLine();  
    }  
}  

Scanner還可以很方便的掃描文件，讀取裡面的信息並轉換成你要的類型，比如對“2 2.2 3.3 3.33 4.5 done”這樣的數據求和,見如下代碼:

  
public class TestConsole4 {  
  
    public static void main(String[] args) throws IOException {  
        FileWriter fw = new FileWriter("num.txt");  
        fw.write("2 2.2 3.3 3.33 4.5 done");  
        fw.close();  
  
        System.out.println("Sum is "+scanFileForSum("num.txt"));  
    }  
  
    public static double scanFileForSum(String fileName) throws IOException {  
        double sum = 0.0;  
        FileReader fr = null;  
        try {  
            fr = new FileReader(fileName);  
            Scanner scanner = new Scanner(fr);  
              
            while (scanner.hasNext()) {  
                if (scanner.hasNextDouble()) {  
                    sum = sum + scanner.nextDouble();  
  
                } else {  
                    String str = scanner.next();  
  
                    if (str.equals("done")) {  
                        break;  
                    } else {  
                        throw new RuntimeException("File Format is wrong!");  
                    }  
  
                }  
            }  
  
        } catch (FileNotFoundException e) {  
            throw new RuntimeException("File " + fileName + " not found!");  
        } finally {  
            if (fr != null)  
                fr.close();  
        }  
        return sum;  
    }  
}