JAVA 缓存数组之----ByteArrayOutputStream类详解

雨点打透心脏的1/2处 2022-06-14 01:19 326阅读 0赞

## Java ByteArrayOutputStream类 ##

字节数组输出流在内存中创建一个字节数组缓冲区，所有发送到输出流的数据保存在该字节数组缓冲区中。创建字节数组输出流对象有以下几种方式。

下面的构造方法创建一个32字节（默认大小）的缓冲区。

OutputStream bOut = new ByteArrayOutputStream();

另一个构造方法创建一个大小为n字节的缓冲区。

OutputStream bOut = new ByteArrayOutputStream(int a)

成功创建字节数组输出流对象后，可以参见以下列表中的方法，对流进行写操作或其他操作。

<table style="margin:4px 0px; padding:0px; width:818px; table-layout:fixed; border-collapse:collapse; border-spacing:0px; color:rgb(0,0,0); font-family:Verdana,Arial,Helvetica,sans-serif; font-size:13px; line-height:22.1px"> 
 <tbody style="margin:0px; padding:0px"> 
  <tr style="margin:0px; padding:0px; background-color:rgb(239,239,239)"> 
   <th style="margin:0px; padding:3px; border-top-width:1px; border-right-width:1px; border-left-width:1px; border-style:solid solid none; border-top-color:rgb(189,189,189); border-right-color:rgb(189,189,189); border-left-color:rgb(189,189,189); color:rgb(255,255,255); font-size:14px; vertical-align:top; width:73px; background-color:rgb(189,189,189)"> 序号</th> 
   <th style="margin:0px; padding:3px; border-top-width:1px; border-right-width:1px; border-left-width:1px; border-style:solid solid none; border-top-color:rgb(189,189,189); border-right-color:rgb(189,189,189); border-left-color:rgb(189,189,189); color:rgb(255,255,255); font-size:14px; vertical-align:top; width:508px; background-color:rgb(189,189,189)"> 方法描述</th> 
  </tr> 
  <tr style="margin:0px; padding:0px"> 
   <td style="margin:0px; padding:7px 5px; min-width:40px; height:30px; border:1px solid rgb(221,221,221); vertical-align:top; font-size:14px; width:73px"> 1</td> 
   <td style="margin:0px; padding:7px 5px; min-width:40px; height:30px; border:1px solid rgb(221,221,221); vertical-align:top; font-size:14px; width:508px"> <span style="margin:0px; padding:0px">public void reset()</span><br style="margin:0px; padding:0px"> 将此字节数组输出流的&nbsp;<code style="margin:0px 5px; padding:0px 4px; display:inline-block; font-size:13px; color:rgb(199,37,78); font-family:Consolas,'Courier New',Courier,monospace; background-color:rgb(249,242,244)">count</code>&nbsp;字段重置为零，从而丢弃输出流中目前已累积的所有数据输出。</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; background-color:rgb(239,239,239)"> 
   <td style="margin:0px; padding:7px 5px; min-width:40px; height:30px; border:1px solid rgb(221,221,221); vertical-align:top; font-size:14px; width:73px"> 2</td> 
   <td style="margin:0px; padding:7px 5px; min-width:40px; height:30px; border:1px solid rgb(221,221,221); vertical-align:top; font-size:14px; width:508px"> <span style="margin:0px; padding:0px">public byte[] toByteArray()</span><br style="margin:0px; padding:0px"> 创建一个新分配的字节数组。数组的大小和当前输出流的大小，内容是当前输出流的拷贝。</td> 
  </tr> 
  <tr style="margin:0px; padding:0px"> 
   <td style="margin:0px; padding:7px 5px; min-width:40px; height:30px; border:1px solid rgb(221,221,221); vertical-align:top; font-size:14px; width:73px"> 3</td> 
   <td style="margin:0px; padding:7px 5px; min-width:40px; height:30px; border:1px solid rgb(221,221,221); vertical-align:top; font-size:14px; width:508px"> <span style="margin:0px; padding:0px">public String toString()</span><br style="margin:0px; padding:0px"> 将缓冲区的内容转换为字符串，根据平台的默认字符编码将字节转换成字符。</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; background-color:rgb(239,239,239)"> 
   <td style="margin:0px; padding:7px 5px; min-width:40px; height:30px; border:1px solid rgb(221,221,221); vertical-align:top; font-size:14px; width:73px"> 4</td> 
   <td style="margin:0px; padding:7px 5px; min-width:40px; height:30px; border:1px solid rgb(221,221,221); vertical-align:top; font-size:14px; width:508px"> <span style="margin:0px; padding:0px">public void write(int w)</span><br style="margin:0px; padding:0px"> &nbsp;将指定的字节写入此字节数组输出流。</td> 
  </tr> 
  <tr style="margin:0px; padding:0px"> 
   <td style="margin:0px; padding:7px 5px; min-width:40px; height:30px; border:1px solid rgb(221,221,221); vertical-align:top; font-size:14px; width:73px"> 5</td> 
   <td style="margin:0px; padding:7px 5px; min-width:40px; height:30px; border:1px solid rgb(221,221,221); vertical-align:top; font-size:14px; width:508px"> <span style="margin:0px; padding:0px">public void write(byte []b, int of, int len)</span><br style="margin:0px; padding:0px"> &nbsp;将指定字节数组中从偏移量&nbsp;<code style="margin:0px 5px; padding:0px 4px; display:inline-block; font-size:13px; color:rgb(199,37,78); font-family:Consolas,'Courier New',Courier,monospace; background-color:rgb(249,242,244)">off</code>&nbsp;开始的&nbsp;<code style="margin:0px 5px; padding:0px 4px; display:inline-block; font-size:13px; color:rgb(199,37,78); font-family:Consolas,'Courier New',Courier,monospace; background-color:rgb(249,242,244)">len</code>&nbsp;个字节写入此字节数组输出流。</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; background-color:rgb(239,239,239)"> 
   <td style="margin:0px; padding:7px 5px; min-width:40px; height:30px; border:1px solid rgb(221,221,221); vertical-align:top; font-size:14px; width:73px"> 6</td> 
   <td style="margin:0px; padding:7px 5px; min-width:40px; height:30px; border:1px solid rgb(221,221,221); vertical-align:top; font-size:14px; width:508px"> <span style="margin:0px; padding:0px">public void writeTo(OutputStream outSt)</span><br style="margin:0px; padding:0px"> 将此字节数组输出流的全部内容写入到指定的输出流参数中。</td> 
  </tr> 
 </tbody> 
</table>

### 实例 ###

下面的例子演示了ByteArrayInputStream 和 ByteArrayOutputStream的使用：

import java.io.*;
    public class ByteStreamTest {
       public static void main(String args[])throws IOException {
          ByteArrayOutputStream bOutput = new ByteArrayOutputStream(12);
          while( bOutput.size()!= 10 ) {
             // 获取用户输入
             bOutput.write(System.in.read()); 
          }
          byte b [] = bOutput.toByteArray();
          System.out.println("Print the content");
          for(int x= 0 ; x < b.length; x++) {          // 打印字符          System.out.print((char)b[x]  + "   ");        }       System.out.println("   ");       int c;       ByteArrayOutputStream bInput = new ByteArrayOutputStream(b);       System.out.println("Converting characters to Upper case " );       for(int y = 0 ; y < 1; y++ ) {          while(( c= bInput.read())!= -1) {             System.out.println(Character.toUpperCase((char)c));          }          bInput.reset();        }    } }

以上实例编译运行结果如下：

asdfghjkly
    Print the content
    a   s   d   f   g   h   j   k   l   y
    Converting characters to Upper case
    A
    S
    D
    F
    G
    H
    J
    K
    L
    Y