1. 使用 JDK 5 的 Scanner
package cc.unmi.test; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.InputStream; import java.util.Scanner; /** * * @author Unmi * @Creation date: 2013-02-01 */ public class Test { /** * @param args * @throws FileNotFoundException */ public static void main(String[] args) throws FileNotFoundException { InputStream inputStream = new FileInputStream("d:/sample.txt"); Scanner scanner = new Scanner(inputStream, "UTF-8"); String text = scanner.useDelimiter("\\A").next(); System.out.println(text); scanner.close(); } }
2. JDK1.4 及之前的 BufferedReader 法
package cc.unmi.test; import java.io.BufferedReader; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; /** * * @author Unmi * @Creation date: 2013-02-01 */ public class Test { /** * @param args * @throws IOException */ public static void main(String[] args) throws IOException { InputStream inputStream = new FileInputStream("d:/sample.txt"); StringBuilder stringBuilder = new StringBuilder(); BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream)); boolean firstLine = true; String line = null; ; while((line = bufferedReader.readLine()) != null){ if(!firstLine){ stringBuilder.append(System.getProperty("line.separator")); }else{ firstLine = false; } stringBuilder.append(line); } System.out.println(stringBuilder.toString()); } }
中间那些判断是不是第一行来决定是否加换行符是些杂音。
3. JDK1.4 及之前的 readBytes 法
package cc.unmi.test; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; /** * * @author Unmi * @Creation date: 2013-02-01 */ public class Test { /** * @throws IOException */ public static void main(String[] args) throws IOException { InputStream inputStream = new FileInputStream("d:/sample.txt"); byte[] buffer = new byte[2048]; int readBytes = 0; StringBuilder stringBuilder = new StringBuilder(); while((readBytes = inputStream.read(buffer)) > 0){ stringBuilder.append(new String(buffer, 0, readBytes)); } System.out.println(stringBuilder.toString()); } }
缓冲区的大小自己根据实际来调,比 BufferedReader 还简洁些,不需管换行符的事情。
4. Apache commons IOUtils.toString 法
package cc.unmi.test; import java.io.*; import org.apache.commons.io.IOUtils; /** * * @author Unmi * @Creation date: 2013-02-01 */ public class Test { /** * @throws IOException */ public static void main(String[] args) throws IOException { InputStream inputStream = new FileInputStream("d:/sample.txt"); String text = IOUtils.toString(inputStream); System.out.println(text); } }
第三方库就是第三方库,人家充分考虑到了你的感受,你对 JDK 库的抱怨,多简洁,一行搞定。IOUtils 还能把内容拷入其他的 Writer 中,如 IOUtils.copy(inputStream, new StringWriter())。
5. Google guava 的 CharStreams 方法
package cc.unmi.test; import java.io.*; import com.google.common.io.CharStreams; /** * * @author Unmi * @Creation date: 2013-02-01 */ public class Test { /** * @throws IOException */ public static void main(String[] args) throws IOException { InputStream inputStream = new FileInputStream("d:/sample.txt"); String text = CharStreams.toString(new InputStreamReader(inputStream, "UTF-8")); System.out.println(text); } }
CharSteams 不是直接作用在 InputSteam 上的,还要靠 InputStreamReader 拱个桥。
6. JDK 7 的 NIO readAllBytes
package cc.unmi.test; import java.io.IOException; import java.nio.file.*; /** * * @author Unmi * @Creation date: 2013-02-01 */ public class Test { /** * @throws IOException */ public static void main(String[] args) throws IOException { byte[] bytes = Files.readAllBytes(Paths.get("d:/sample.txt")); String text = new String(bytes); System.out.println(text); } }
这让我们相信 JDK 一直还有人在管,虽然不可能象动态语言的方法那么快捷,上面的 readAllBytes 在处理大文件时肯定会很被动的。而 Files.readAllLines 会把文件的内容读入一个 List<String> 对象中,往内存不断放东西就得掂量下内存会不会被爆。在 java.nio.file.* 还有很多新事物可供发掘。