這裡記錄Java中從控制臺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; } } 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 www.aiwalls.com
*/
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(); } } 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; } } 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;
}
}
(3)JDK 1.6（利用java.io.Console進行讀取）
JDK6中提供瞭java.io.Console類專用來訪問基於字符的控制臺設備.
你的程序如果要與Windows下的cmd或者Linux下的Terminal交互,就可以用Console類代勞.（類似System.in和System.out）
但我們不總是能得到可用的Console, 一個JVM是否有可用的Console依賴於底層平臺和JVM如何被調用.
如果JVM是在交互式命令行(比如Windows的cmd)中啟動的,並且輸入輸出沒有重定向到另外的地方,那麼就可以得到一個可用的Console實例。
在使用 IDE 的情況下，是無法獲取到Console實例的，原因在於在 IDE 的環境下，重新定向瞭標準輸入和輸出流，也是就是將系統控制臺上的輸入輸出重定向到瞭 IDE 的控制臺中
public class TestConsole3 { public static void main(String[] args) { String str = readDataFromConsole("Please input string:"); System.out.println("The information from console:" + str); } /** * Use java.io.console to read data from console * * @param prompt * * @return input string */ private static String readDataFromConsole(String prompt) { Console console = System.console(); if (console == null) { throw new IllegalStateException("Console is not available!"); } return console.readLine(prompt); } } public class TestConsole3 {
public static void main(String[] args) {
String str = readDataFromConsole("Please input string:");
System.out.println("The information from console:" + str);
}
/**
* Use java.io.console to read data from console
*
* @param prompt
*
* @return input string
*/
private static String readDataFromConsole(String prompt) {
Console console = System.console();
if (console == null) {
throw new IllegalStateException("Console is not available!");
}
return console.readLine(prompt);
}
}
Console類還有個特色就是，專門對密碼(輸入無回顯)等安全字符，進行瞭處理。專門提供 readPassword()方法,具體應用見如下代碼：
public class TestConsole5 { public static void main(String[] args) { Console console = System.console(); if (console == null) { throw new IllegalStateException("Console is not available!"); } while(true){ String username = console.readLine("Username: "); char[] password = console.readPassword("Password: "); if (username.equals("Chris") && String.valueOf(password).equals("GoHead")) { console.printf("Welcome to Java Application %1$s.\n", username); // 使用後應立即將數組清空，以減少其在內存中占用的時間，增強安全性 password = null; System.exit(-1); } else { console.printf("Invalid username or password.\n"); } } } }
摘自 qiaoning13256的專欄