java中有没有办法从byte []读取/写入整数,布尔和字符串?
Like:
write(50550);
write(true);
write("bla bla");
And then:
int i = readInt();
int j = readBoolean();
String res = readUTF();
Walter和fge回答了两种不同的方式来实现这个目标。唯一的问题仍然存在:“哪种方式更快?”
答案 0 :(得分:4)
您要找的是DataInputStream
和DataOutputStream
。
两者都包裹resp.an InputStream
和OutputStream
,可以读/写各种基本类型,“转换的UTF”数据等。
至于写入一个字节数组本身,你想使用ByteArrayOutputStream
,并将DataOutputStream
包裹在它上面:
final ByteArrayOutputStream out = new ByteArrayOutputStream();
final DataOutputStream dataOut = new DataOutputStream(out);
// use dataOut; then:
final ByteArrayInputStream in = new ByteArrayInputStream(out.toByteArray());
final DataInputStream dataIn = new DataInputStream(in);
// read back
无论如何,在你的一条评论中,还不清楚你想做什么;如果这只是二进制数据,则转而使用ByteBuffer
;您可以在使用它之前随意更改其字节序(默认情况下是大端),在其中包装字节数组等等......不同之处在于Java没有无符号原始整数类型(嗯,保存为{{1但这个是一个奇特的野兽。)
总而言之,这看起来像一个XY问题,所以我建议你编辑你的问题并完全解释你想要做什么。
答案 1 :(得分:2)
ByteBuffer buffer = ByteBuffer.allocate(0x1000);
buffer.order(ByteOrder.BIG_ENDIAN);
buffer.putInt(100);
//store booleans as 1 or 0 in a byte
buffer.put((byte) (true ? 1 : 0));
buffer.put((byte) (false ? 1 : 0));
//store string as [int length, byte array]
String str = "Hello World!";
byte[] strBytes = str.getBytes(StandardCharsets.UTF_8); //use any charset you want here
buffer.putInt(strBytes.length);
buffer.put(strBytes);
buffer.flip();
byte[] data = new byte[buffer.remaining()];
buffer.get(data);
System.out.println("Total Bytes: " + data.length);
ByteBuffer bb = ByteBuffer.wrap(data);
System.out.println(bb.getInt());
System.out.println(bb.get() != 0);
System.out.println(bb.get() != 0);
byte[] inStr = new byte[bb.getInt()];
bb.get(inStr);
String myStr = new String(inStr, StandardCharsets.UTF_8);
System.out.println(myStr);
答案 2 :(得分:0)
您似乎正在从DataInputStream和DataOutputStream中搜索。
ByteArrayOutputStream baos = new ByteArrayOutputStream();
DataOutputStream dos = new DataOutputStream(baos);
// Like:
dos.writeInt(50550);
dos.writeBoolean(true);
dos.writeUTF("bla bla");
byte[] bytes = baos.toByteArray();
DataInputStream dis = new DataInputStream(new ByteArrayInputStream(bytes));
// And then:
int i = dis.readInt();
boolean flag = dis.readBoolean();
String res = dis.readUTF();
System.out.println("i: " + i + ", flag: " + flag + ", res: '" + res + "'");
打印
i: 50550, flag: true, res: 'bla bla'
stdext :: writeULE16,stdext :: writeULE32,stdext :: writeULE64和stdext :: readULE16,stdext :: readULE32,stdext :: readULE64
这意味着您需要一种文本格式,在这种情况下我建议使用PrintWriter
ByteArrayOutputStream baos = new ByteArrayOutputStream();
PrintWriter pw = new PrintWriter(new OutputStreamWriter(baos, "UTF-16LE"));
// Like:
pw.println(50550);
pw.println(true);
pw.println("bla bla");
pw.close();
byte[] bytes = baos.toByteArray();
Scanner in = new Scanner(new InputStreamReader(new ByteArrayInputStream(bytes), "UTF-16LE"));
// And then:
int i = in.nextInt();
boolean flag = in.nextBoolean(); in.nextLine(); // discard the rest of the line
String res = in.nextLine();
System.out.println("i: " + i + ", flag: " + flag + ", res: '" + res + "'");
打印相同的内容,但底层字节将采用UTF-16LE编码。这种方法还支持UTF-16BE,UTF-32LE,UTF-32BE(和UTF-8)