这几天遇到一个转换问题,是要把128位的hash与String互转,hash 用byte[]存,16个字节,hash在数据库中用binary(128)类型存。
简单的来说,假设有一个byte[] by = {0x01,0x02,0x03},需要转换城的string就是:"000000010000000200000003";
同样,假设读出的string是"000010000000100100001010",那么转成的byte[] 就是{0x08,0x09,0x0a}.
getbytes()和toString()方法根本不行,而且这两个的转换操作要尽可能高效,求高手,求教育~
简单的来说,假设有一个byte[] by = {0x01,0x02,0x03},需要转换城的string就是:"000000010000000200000003";
同样,假设读出的string是"000010000000100100001010",那么转成的byte[] 就是{0x08,0x09,0x0a}.
getbytes()和toString()方法根本不行,而且这两个的转换操作要尽可能高效,求高手,求教育~
int i = bytes[0];int j=bytes[1] ;int k=bytes[2];
String s1= Integer.toBinaryString(i);
String s2= Integer.toBinaryString(j);
String s3= Integer.toBinaryString(k);
StringBuffer sb = new StringBuffer("000000000");
System.out.println(
sb.toString().substring(0,8-s1.length())+s1+
sb.toString().substring(0,8-s2.length())+s2+
sb.toString().substring(0,8-s3.length())+s3);
// byte to String
byte b = 0x08;
int i = ((Byte)b).intValue();
System.out.println(i);
String s = Integer.toBinaryString(i);
System.out.println(s);
// String to byte
String s2 = "00001000";
// 按二进制转换s2
byte b2 = Byte.parseByte(s2, 2);
System.out.println(b2);
刚才测了下,在不打印的情况下,两个方法执行一次用时2.4013782070000002E-6秒
public class Test {
public static void main(String[] args) {
long start = System.nanoTime();
//不输出结果运行1000000次
for(int i = 0;i < 1e6;i++){
byte[] bys = {0x01,0x02,0x03};
bytesToString(bys);
//System.out.println(bytesToString(bys));
byte[] bys2 = stringTobytes("000010000000100100001010");
//for(byte b:bys2)
//System.out.println(b);
}
long end = System.nanoTime();
System.out.println("time:" + (end - start) / 1e9 + "s");
System.out.println("pre time:" + (end - start) / 1e9 / 1e6 + "s");
}
private static String bytesToString(byte[] bys){
StringBuffer sb = new StringBuffer();
for(int i = 0;i < bys.length;i++){
String s = String.valueOf(bys[i]);
for(int j = 0;j < Byte.SIZE - s.length();j++)
sb.append("0");
sb.append(s);
}
return sb.toString();
}
private static byte[] stringTobytes(String str){
byte[] bys = new byte[str.length() / Byte.SIZE];
for(int i = 0;i < bys.length;i++){
String s = str.substring(i * Byte.SIZE,(i + 1) * Byte.SIZE);
for(int j = 0;j < s.length();j++){
if(s.charAt(j) == '1')
bys[i] |= (1 << (Byte.SIZE - j - 1));
}
}
return bys;
}
}