Java如何讀取文件內容再編輯
- SUN認證
- 關注:1.15W次
有時候,我們需要將讀取文件的.內容到一個byte[] 數組中,然後對這個數組進行一些修改,這時,我們可以藉助於ByteArrayOutputStream 這個類來實現。
ByteArrayOutputStream,顧名思義,同樣是一個OutputStream,那麼,對於它的寫入操作,和其他的 OutputStream應該是沒有什麼兩樣,寫入代碼可以説是隨手拈來的,與其他輸出流的不同之處在於,ByteArrayOutputStream寫入到內存中,並提供一個 toByteArray() 方法返回我們所需要的byte[]。
Java代碼
//保存上傳的附件信息
String filename = files[0];
String filepath = "upload/append/"+files[1];
BufferedInputStream in = new BufferedInputStream(new FileInputStream(filepath));
ByteArrayOutputStream out = new ByteArrayOutputStream(2048);
tln("available bytes"+lable());
byte[] temp = new byte[2048];
int size =0;
while((size = (temp))!=-1){ e(temp,0,size);
}
e();
byte[] content = teArray();
String stream = new BaseCode64()deBase64(content);
tln("content" +th);
effect += insertAttachmentInfo(conn,attNo,processId,filename,stream);
這裏把讀取的流以base64保存,使用了類BaseCode64()的方法EncodeBase64。
代碼如下:
Java代碼
package ;
import ArrayOutputStream;
public class BaseCode64 {
private String TableBase64;
private String FError;
public BaseCode64()
{
TableBase64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
FError = new String();
FError = "";
}
public String DecodeBase64(byte [] Value){
ByteArrayOutputStream o = new ByteArrayOutputStream();
byte d[] = new byte[4];
try
{
int count = 0;
byte x[] = Value;
do
{
if(count >= th)
{
break;
}
for(int n = 0; n <= 3; n++)
{
if(count >= th)
{
d[n] = 64;
} else
{
int y = xOf(x[count]);
if(y < 0)
{
y = 65;
}
d[n] = (byte)y;
}
count++;
}
e((byte)(((d[0] & 0x3f) << 2) + ((d[1] & 0x30) >> 4)));
if(d[2] != 64)
{
e((byte)(((d[1] & 0xf) << 4) + ((d[2] & 0x3c) >> 2)));
if(d[3] != 64)
{
e((byte)(((d[2] & 3) << 6) + (d[3] & 0x3f)));
}
}
} while(true);
}
catch(StringIndexOutOfBoundsException e)
{
FError = eOf(eOf(FError)) + eOf(eOf(ring()));
tln(ring());
}
return ring();
}
public String EncodeBase64(byte [] Value){
ByteArrayOutputStream o = new ByteArrayOutputStream();
byte d[] = new byte[4];
try
{
int count = 0;
for(byte x[] = Value; count < th;)
{
byte c = x[count];
count++;
d[0] = (byte)((c & 0xfc) >> 2);
d[1] = (byte)((c & 3) << 4);
if(count < th)
{
c = x[count];
count++;
d[1] = (byte)(d[1] + (byte)((c & 0xf0) >> 4));
d[2] = (byte)((c & 0xf) << 2);
if(count < th)
{
c = x[count];
count++;
d[2] = (byte)(d[2] + ((c & 0xc0) >> 6));
d[3] = (byte)(c & 0x3f);
} else
{
d[3] = 64;
}
} else
{
d[2] = 64;
d[3] = 64;
}
int n = 0;
while(n <= 3)
{
e(At(d[n]));
n++;
}
}
}
catch(StringIndexOutOfBoundsException e)
{
FError = eOf(eOf(FError)) + eOf(eOf(ring()));
tln(ring());
}
return ring();
}
}
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