public class Test {
    public static void main(String[] args) throws IOException {
　　// 最好別用FileReader，容易漏讀
        // 如果是window系統，/需要換成\
        FileInputStream in = new FileInputStream("/Users/mac/eclipse-workspace/Demo/src/Test/file.txt");
        byte[] buffer = new byte[1024];
        
        int len = 0;
        while((len=in.read(buffer))!=-1) {
            System.out.println(new String(buffer,0,len));
        }
        
        in.close(); // 一定記得關閉！
 
    }
}

public class Try {

    public static void main(String[] args) throws IOException {
        File file = new File("/Users/mac/Desktop/1.txt");
        BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(file), "utf-8"));
        while (true) {
            String line = reader.readLine();
            if(line==null) {break;}
            System.out.println(line);
        }
    }
}

/*
     * 目標：把1.txt內容復制到2.txt
     */
    File file = new File("/Users/mac/Desktop/1.txt");
    File file2 = new File("/Users/mac/Desktop/2.txt");
    @Test
    public void test1() throws IOException {
        FileInputStream in = new FileInputStream(file);
        FileOutputStream out = new FileOutputStream(file2);
        int len = 0;
        byte[] buffer = new byte[1024];
        while ((len = in.read(buffer)) != -1) {
            out.write(buffer, 0, len);
        }
    }