Java核心类库-IO-随机访问文件（RandomAccessFile）

<span style="font-size: 14px"><span style="color: #0000ff">public</span> <span style="color: #0000ff">class</span><span style="color: #000000"> RandomAccessFileDemo
{
    </span><span style="color: #0000ff">public</span> <span style="color: #0000ff">static</span> <span style="color: #0000ff">void</span> main(String[] args) <span style="color: #0000ff">throws</span><span style="color: #000000"> Exception {
        File f </span>= <span style="color: #0000ff">new</span> File("raf.txt"<span style="color: #000000">);
        </span><span style="color: #008000">//</span><span style="color: #008000">write(f);</span>
<span style="color: #000000">        read(f);
    }

    </span><span style="color: #0000ff">private</span> <span style="color: #0000ff">static</span> <span style="color: #0000ff">void</span> read(File f) <span style="color: #0000ff">throws</span><span style="color: #000000"> Exception {
        </span><span style="color: #008000">//</span><span style="color: #008000">r表示只读</span>
        RandomAccessFile raf = <span style="color: #0000ff">new</span> RandomAccessFile(f,"r"<span style="color: #000000">);
        System.out.println(</span>"文件指针位置："+ raf.getFilePointer());<span style="color: #008000">//</span><span style="color: #008000">0</span>
        <span style="color: #0000ff">byte</span> b =<span style="color: #000000"> raf.readByte();
        System.out.println(b);</span><span style="color: #008000">//</span><span style="color: #008000">64</span>
        System.out.println("文件指针位置："+ raf.getFilePointer());<span style="color: #008000">//</span><span style="color: #008000">1</span>
        String str =<span style="color: #000000"> raf.readUTF();
        System.out.println(str);</span><span style="color: #008000">//</span><span style="color: #008000">邓肯</span>
        System.out.println("文件指针位置："+ raf.getFilePointer());<span style="color: #008000">//</span><span style="color: #008000">9</span>
        raf.seek(0);<span style="color: #008000">//</span><span style="color: #008000">设置文件指针位置</span>
        System.out.println("文件指针位置："+ raf.getFilePointer());<span style="color: #008000">//</span><span style="color: #008000">0</span>
        raf.skipBytes(9);<span style="color: #008000">//</span><span style="color: #008000">设置文件指针跳过9个字节</span>
        System.out.println("文件指针位置："+ raf.getFilePointer());<span style="color: #008000">//</span><span style="color: #008000">9</span>
        <span style="color: #0000ff">int</span> i =<span style="color: #000000"> raf.readInt();
        System.out.println(i);
        System.out.println(</span>"文件指针位置："+ raf.getFilePointer());<span style="color: #008000">//</span><span style="color: #008000">13</span>
<span style="color: #000000">        raf.close();
    }

    </span><span style="color: #0000ff">private</span> <span style="color: #0000ff">static</span> <span style="color: #0000ff">void</span> write(File f) <span style="color: #0000ff">throws</span><span style="color: #000000"> Exception {
        </span><span style="color: #008000">//</span><span style="color: #008000">rw表示读写</span>
        RandomAccessFile raf = <span style="color: #0000ff">new</span> RandomAccessFile(f,"rw"<span style="color: #000000">);
        raf.writeByte(</span>65<span style="color: #000000">);
        raf.writeUTF(</span>"邓肯");<span style="color: #008000">//</span><span style="color: #008000">使用的是修改之后的UTF-8，多两个字节</span>
        raf.writeInt(20<span style="color: #000000">);
        raf.close();
    }
}</span></span>

RandomAccessFile经常用来做多线程下载：

1. 多线程

2. 多点下载

Java核心类库-IO-随机访问文件（RandomAccessFile）

标签：类库   字节   java   取数据   file   strong   except   txt   ati   

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