我有一个字节数组。 我希望将该数组的每个字节String转换为相应的十六进制值。
Java中是否有将字节数组转换为十六进制的函数?
当前回答
如果存在性能问题，创建(并销毁)一堆String实例并不是一个好方法。
请忽略那些冗长(重复)参数检查语句(if)。那是为了(另一个)教育目的。
完整的maven项目:http://jinahya.googlecode.com/svn/trunk/com.googlecode.jinahya/hex-codec/
编码…
/**
* Encodes a single nibble.
*
* @param decoded the nibble to encode.
*
* @return the encoded half octet.
*/
protected static int encodeHalf(final int decoded) {
switch (decoded) {
case 0x00:
case 0x01:
case 0x02:
case 0x03:
case 0x04:
case 0x05:
case 0x06:
case 0x07:
case 0x08:
case 0x09:
return decoded + 0x30; // 0x30('0') - 0x39('9')
case 0x0A:
case 0x0B:
case 0x0C:
case 0x0D:
case 0x0E:
case 0x0F:
return decoded + 0x57; // 0x41('a') - 0x46('f')
default:
throw new IllegalArgumentException("illegal half: " + decoded);
}
}
/**
* Encodes a single octet into two nibbles.
*
* @param decoded the octet to encode.
* @param encoded the array to which each encoded nibbles are written.
* @param offset the offset in the array.
*/
protected static void encodeSingle(final int decoded, final byte[] encoded,
final int offset) {
if (encoded == null) {
throw new IllegalArgumentException("null encoded");
}
if (encoded.length < 2) {
// not required
throw new IllegalArgumentException(
"encoded.length(" + encoded.length + ") < 2");
}
if (offset < 0) {
throw new IllegalArgumentException("offset(" + offset + ") < 0");
}
if (offset >= encoded.length - 1) {
throw new IllegalArgumentException(
"offset(" + offset + ") >= encoded.length(" + encoded.length
+ ") - 1");
}
encoded[offset] = (byte) encodeHalf((decoded >> 4) & 0x0F);
encoded[offset + 1] = (byte) encodeHalf(decoded & 0x0F);
}
/**
* Decodes given sequence of octets into a sequence of nibbles.
*
* @param decoded the octets to encode
*
* @return the encoded nibbles.
*/
protected static byte[] encodeMultiple(final byte[] decoded) {
if (decoded == null) {
throw new IllegalArgumentException("null decoded");
}
final byte[] encoded = new byte[decoded.length << 1];
int offset = 0;
for (int i = 0; i < decoded.length; i++) {
encodeSingle(decoded[i], encoded, offset);
offset += 2;
}
return encoded;
}
/**
* Encodes given sequence of octets into a sequence of nibbles.
*
* @param decoded the octets to encode.
*
* @return the encoded nibbles.
*/
public byte[] encode(final byte[] decoded) {
return encodeMultiple(decoded);
}
解码…
/**
* Decodes a single nibble.
*
* @param encoded the nibble to decode.
*
* @return the decoded half octet.
*/
protected static int decodeHalf(final int encoded) {
switch (encoded) {
case 0x30: // '0'
case 0x31: // '1'
case 0x32: // '2'
case 0x33: // '3'
case 0x34: // '4'
case 0x35: // '5'
case 0x36: // '6'
case 0x37: // '7'
case 0x38: // '8'
case 0x39: // '9'
return encoded - 0x30;
case 0x41: // 'A'
case 0x42: // 'B'
case 0x43: // 'C'
case 0x44: // 'D'
case 0x45: // 'E'
case 0x46: // 'F'
return encoded - 0x37;
case 0x61: // 'a'
case 0x62: // 'b'
case 0x63: // 'c'
case 0x64: // 'd'
case 0x65: // 'e'
case 0x66: // 'f'
return encoded - 0x57;
default:
throw new IllegalArgumentException("illegal half: " + encoded);
}
}
/**
* Decodes two nibbles into a single octet.
*
* @param encoded the nibble array.
* @param offset the offset in the array.
*
* @return decoded octet.
*/
protected static int decodeSingle(final byte[] encoded, final int offset) {
if (encoded == null) {
throw new IllegalArgumentException("null encoded");
}
if (encoded.length < 2) {
// not required
throw new IllegalArgumentException(
"encoded.length(" + encoded.length + ") < 2");
}
if (offset < 0) {
throw new IllegalArgumentException("offset(" + offset + ") < 0");
}
if (offset >= encoded.length - 1) {
throw new IllegalArgumentException(
"offset(" + offset + ") >= encoded.length(" + encoded.length
+ ") - 1");
}
return (decodeHalf(encoded[offset]) << 4)
| decodeHalf(encoded[offset + 1]);
}
/**
* Encodes given sequence of nibbles into a sequence of octets.
*
* @param encoded the nibbles to decode.
*
* @return the encoded octets.
*/
protected static byte[] decodeMultiple(final byte[] encoded) {
if (encoded == null) {
throw new IllegalArgumentException("null encoded");
}
if ((encoded.length & 0x01) == 0x01) {
throw new IllegalArgumentException(
"encoded.length(" + encoded.length + ") is not even");
}
final byte[] decoded = new byte[encoded.length >> 1];
int offset = 0;
for (int i = 0; i < decoded.length; i++) {
decoded[i] = (byte) decodeSingle(encoded, offset);
offset += 2;
}
return decoded;
}
/**
* Decodes given sequence of nibbles into a sequence of octets.
*
* @param encoded the nibbles to decode.
*
* @return the decoded octets.
*/
public byte[] decode(final byte[] encoded) {
return decodeMultiple(encoded);
}
其他回答
就像其他答案一样，我建议使用String.format()和BigInteger。但是要将字节数组解释为大端二进制表示，而不是双补二进制表示(使用signum和不完全使用可能的十六进制值范围)，请使用BigInteger(int signum, byte[] magnitude)，而不是BigInteger(byte[] val)。
例如，对于长度为8的字节数组，使用:
String.format("%016X", new BigInteger(1,bytes))
优点:
前导零 没有符号 只有内置函数 只有一行代码
劣势:
也许有更有效的方法
例子:
byte[] bytes = new byte[8];
Random r = new Random();
System.out.println("big-endian | two's-complement");
System.out.println("-----------------|-----------------");
for (int i = 0; i < 10; i++) {
r.nextBytes(bytes);
System.out.print(String.format("%016X", new BigInteger(1,bytes)));
System.out.print(" | ");
System.out.print(String.format("%016X", new BigInteger(bytes)));
System.out.println();
}
示例输出:
big-endian | two's-complement
-----------------|-----------------
3971B56BC7C80590 | 3971B56BC7C80590
64D3C133C86CCBDC | 64D3C133C86CCBDC
B232EFD5BC40FA61 | -4DCD102A43BF059F
CD350CC7DF7C9731 | -32CAF338208368CF
82CDC9ECC1BC8EED | -7D3236133E437113
F438C8C34911A7F5 | -BC7373CB6EE580B
5E99738BE6ACE798 | 5E99738BE6ACE798
A565FE5CE43AA8DD | -5A9A01A31BC55723
032EBA783D2E9A9F | 032EBA783D2E9A9F
8FDAA07263217ABA | -70255F8D9CDE8546
byte[] bytes = {-1, 0, 1, 2, 3 };
StringBuilder sb = new StringBuilder();
for (byte b : bytes) {
sb.append(String.format("%02X ", b));
}
System.out.println(sb.toString());
// prints "FF 00 01 02 03 "
另请参阅
java.util.Formatter语法 %(旗帜)(宽度)转换 标记'0' -结果将被填充为零 宽度2 转换'X' -结果被格式化为十六进制整数，大写
看看问题的文本，也有可能是这样要求的:
String[] arr = {"-1", "0", "10", "20" };
for (int i = 0; i < arr.length; i++) {
arr[i] = String.format("%02x", Byte.parseByte(arr[i]));
}
System.out.println(java.util.Arrays.toString(arr));
// prints "[ff, 00, 0a, 14]"
这里的几个答案使用Integer.toHexString(int);这是可行的，但有一些注意事项。由于形参是int型，因此对byte参数执行扩大原语转换，这涉及到符号扩展。
byte b = -1;
System.out.println(Integer.toHexString(b));
// prints "ffffffff"
在Java中有符号的8位字节被符号扩展为32位整型。为了有效地撤销这个符号扩展，可以使用0xFF来屏蔽字节。
byte b = -1;
System.out.println(Integer.toHexString(b & 0xFF));
// prints "ff"
使用toHexString的另一个问题是它不会用零填充:
byte b = 10;
System.out.println(Integer.toHexString(b & 0xFF));
// prints "a"
这两个因素结合起来应该形成字符串。格式解决方案更佳。
参考文献
整型类型和值 对于字节，从-128到127，包括 JLS 5.1.2扩大原语转换
如果你喜欢流，这里有一个格式-连接方法的单表达式版本:
String hex = IntStream.range(0, bytes.length)
.map(i -> bytes[i] & 0xff)
.mapToObj(b -> String.format("%02x", b))
.collect(Collectors.joining());
遗憾的是没有类似Arrays::streamUnsignedBytes这样的方法。
如果存在性能问题，创建(并销毁)一堆String实例并不是一个好方法。
请忽略那些冗长(重复)参数检查语句(if)。那是为了(另一个)教育目的。
完整的maven项目:http://jinahya.googlecode.com/svn/trunk/com.googlecode.jinahya/hex-codec/
编码…
/**
* Encodes a single nibble.
*
* @param decoded the nibble to encode.
*
* @return the encoded half octet.
*/
protected static int encodeHalf(final int decoded) {
switch (decoded) {
case 0x00:
case 0x01:
case 0x02:
case 0x03:
case 0x04:
case 0x05:
case 0x06:
case 0x07:
case 0x08:
case 0x09:
return decoded + 0x30; // 0x30('0') - 0x39('9')
case 0x0A:
case 0x0B:
case 0x0C:
case 0x0D:
case 0x0E:
case 0x0F:
return decoded + 0x57; // 0x41('a') - 0x46('f')
default:
throw new IllegalArgumentException("illegal half: " + decoded);
}
}
/**
* Encodes a single octet into two nibbles.
*
* @param decoded the octet to encode.
* @param encoded the array to which each encoded nibbles are written.
* @param offset the offset in the array.
*/
protected static void encodeSingle(final int decoded, final byte[] encoded,
final int offset) {
if (encoded == null) {
throw new IllegalArgumentException("null encoded");
}
if (encoded.length < 2) {
// not required
throw new IllegalArgumentException(
"encoded.length(" + encoded.length + ") < 2");
}
if (offset < 0) {
throw new IllegalArgumentException("offset(" + offset + ") < 0");
}
if (offset >= encoded.length - 1) {
throw new IllegalArgumentException(
"offset(" + offset + ") >= encoded.length(" + encoded.length
+ ") - 1");
}
encoded[offset] = (byte) encodeHalf((decoded >> 4) & 0x0F);
encoded[offset + 1] = (byte) encodeHalf(decoded & 0x0F);
}
/**
* Decodes given sequence of octets into a sequence of nibbles.
*
* @param decoded the octets to encode
*
* @return the encoded nibbles.
*/
protected static byte[] encodeMultiple(final byte[] decoded) {
if (decoded == null) {
throw new IllegalArgumentException("null decoded");
}
final byte[] encoded = new byte[decoded.length << 1];
int offset = 0;
for (int i = 0; i < decoded.length; i++) {
encodeSingle(decoded[i], encoded, offset);
offset += 2;
}
return encoded;
}
/**
* Encodes given sequence of octets into a sequence of nibbles.
*
* @param decoded the octets to encode.
*
* @return the encoded nibbles.
*/
public byte[] encode(final byte[] decoded) {
return encodeMultiple(decoded);
}
解码…
/**
* Decodes a single nibble.
*
* @param encoded the nibble to decode.
*
* @return the decoded half octet.
*/
protected static int decodeHalf(final int encoded) {
switch (encoded) {
case 0x30: // '0'
case 0x31: // '1'
case 0x32: // '2'
case 0x33: // '3'
case 0x34: // '4'
case 0x35: // '5'
case 0x36: // '6'
case 0x37: // '7'
case 0x38: // '8'
case 0x39: // '9'
return encoded - 0x30;
case 0x41: // 'A'
case 0x42: // 'B'
case 0x43: // 'C'
case 0x44: // 'D'
case 0x45: // 'E'
case 0x46: // 'F'
return encoded - 0x37;
case 0x61: // 'a'
case 0x62: // 'b'
case 0x63: // 'c'
case 0x64: // 'd'
case 0x65: // 'e'
case 0x66: // 'f'
return encoded - 0x57;
default:
throw new IllegalArgumentException("illegal half: " + encoded);
}
}
/**
* Decodes two nibbles into a single octet.
*
* @param encoded the nibble array.
* @param offset the offset in the array.
*
* @return decoded octet.
*/
protected static int decodeSingle(final byte[] encoded, final int offset) {
if (encoded == null) {
throw new IllegalArgumentException("null encoded");
}
if (encoded.length < 2) {
// not required
throw new IllegalArgumentException(
"encoded.length(" + encoded.length + ") < 2");
}
if (offset < 0) {
throw new IllegalArgumentException("offset(" + offset + ") < 0");
}
if (offset >= encoded.length - 1) {
throw new IllegalArgumentException(
"offset(" + offset + ") >= encoded.length(" + encoded.length
+ ") - 1");
}
return (decodeHalf(encoded[offset]) << 4)
| decodeHalf(encoded[offset + 1]);
}
/**
* Encodes given sequence of nibbles into a sequence of octets.
*
* @param encoded the nibbles to decode.
*
* @return the encoded octets.
*/
protected static byte[] decodeMultiple(final byte[] encoded) {
if (encoded == null) {
throw new IllegalArgumentException("null encoded");
}
if ((encoded.length & 0x01) == 0x01) {
throw new IllegalArgumentException(
"encoded.length(" + encoded.length + ") is not even");
}
final byte[] decoded = new byte[encoded.length >> 1];
int offset = 0;
for (int i = 0; i < decoded.length; i++) {
decoded[i] = (byte) decodeSingle(encoded, offset);
offset += 2;
}
return decoded;
}
/**
* Decodes given sequence of nibbles into a sequence of octets.
*
* @param encoded the nibbles to decode.
*
* @return the decoded octets.
*/
public byte[] decode(final byte[] encoded) {
return decodeMultiple(encoded);
}
你可以使用Bouncy Castle Provider库中的方法:
org.bouncycastle.util.encoders.Hex.toHexString(byteArray);
Bouncy Castle Crypto包是一个Java实现 加密算法。这个jar包含JCE提供程序和 用于JDK 1.5的Bouncy Castle Cryptography API的轻量级API JDK 1.8。
Maven的依赖:
<dependency>
<groupId>org.bouncycastle</groupId>
<artifactId>bcprov-jdk15on</artifactId>
<version>1.60</version>
</dependency>
或来自Apache Commons Codec:
org.apache.commons.codec.binary.Hex.encodeHexString(byteArray);
Apache Commons Codec包包含简单的编码器和解码器 用于各种格式，如Base64和十六进制。除了 这些编码器和解码器被广泛使用，编解码器包也有 维护语音编码实用程序的集合。
Maven的依赖:
<dependency>
<groupId>commons-codec</groupId>
<artifactId>commons-codec</artifactId>
<version>1.11</version>
</dependency>
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