[Java] 讀取全部的檔案內容到字串

Scanner

原始碼

1. import java.io.File; 
2. import java.util.Scanner; 
3.  
4. public class TestScanner { 
5.  
6.    public static void main(String[] args) throws Throwable { 
7.        Scanner sc = new Scanner(new File("input.txt"), "UTF8"); 
8.        String inputStr = sc.useDelimiter("\\Z").next(); 
9.        sc.close(); 
10.  
11.        System.out.println(inputStr); 
12.    } 
13. } 

import java.io.File;
import java.util.Scanner;

public class TestScanner {

    public static void main(String[] args) throws Throwable {
        Scanner sc = new Scanner(new File("input.txt"), "UTF8");
        String inputStr = sc.useDelimiter("\\Z").next();
        sc.close();

        System.out.println(inputStr);
    }
}

useDelimiter 是設置讀取的正規表示式分隔符，這裡可以用 "\\A" 或 "\\Z"
\A : 輸入的開始。
\Z : 輸入的結尾去掉結尾符號的部分。


Java 7 readAllBytes

原始碼

1. import static java.nio.file.Files.readAllBytes; 
2. import static java.nio.file.Paths.get; 
3.  
4. public class TestReadAllBytes { 
5.  
6.    public static void main(String[] args) throws Exception { 
7.        String inputStr = new String(readAllBytes(get("input.txt")), "UTF8"); 
8.        System.out.println(inputStr); 
9.    } 
10. } 

import static java.nio.file.Files.readAllBytes;
import static java.nio.file.Paths.get;

public class TestReadAllBytes {

    public static void main(String[] args) throws Exception {
        String inputStr = new String(readAllBytes(get("input.txt")), "UTF8");
        System.out.println(inputStr);
    }
}

Apache Commons IO

原始碼

1. import java.io.File; 
2.  
3. import org.apache.commons.io.FileUtils; 
4.  
5. public class TestReadFileToString { 
6.  
7.    public static void main(String[] args) throws Throwable { 
8.        File file = new File("input.txt"); 
9.        String inputStr = FileUtils.readFileToString(file, "UTF8"); 
10.        System.out.println(inputStr); 
11.    } 
12. } 

import java.io.File;

import org.apache.commons.io.FileUtils;

public class TestReadFileToString {

    public static void main(String[] args) throws Throwable {
        File file = new File("input.txt");
        String inputStr = FileUtils.readFileToString(file, "UTF8");
        System.out.println(inputStr);
    }
}

DataInputStream available

原始碼

1. import java.io.DataInputStream; 
2. import java.io.FileInputStream; 
3.  
4. public class TestDataInputStream { 
5.  
6.    public static void main(String[] args) throws Exception { 
7.  
8.        FileInputStream fileStream = new FileInputStream ("input.txt"); 
9.        DataInputStream dis = new DataInputStream (fileStream); 
10.  
11.        byte[] datainBytes = new byte[dis.available()]; 
12.        dis.readFully(datainBytes); 
13.        dis.close(); 
14.  
15.        String inputStr = new String(datainBytes, "UTF8"); 
16.        System.out.println(inputStr); 
17.    } 
18. } 

import java.io.DataInputStream;
import java.io.FileInputStream;

public class TestDataInputStream {

    public static void main(String[] args) throws Exception {

        FileInputStream fileStream = new FileInputStream ("input.txt");
        DataInputStream dis = new DataInputStream (fileStream);

        byte[] datainBytes = new byte[dis.available()];
        dis.readFully(datainBytes);
        dis.close();

        String inputStr = new String(datainBytes, "UTF8");
        System.out.println(inputStr);
    }
}