java  string 计算原理 code

public int hashCode()
  {
    int i = this.hash;
    if ((i == 0) && (this.value.length > 0))
    {
      char[] arrayOfChar = this.value;
      for (int j = 0; j < this.value.length; ++j)
        i = 31 * i + arrayOfChar[j];
      this.hash = i;
    }
    return i;
  }

java 测试code

public class test_hashcode {
    public static void main(String args[]) {
        String Str = new String("www.runoob.com");
        System.out.println(Str+" ,字符串的哈希码为 :" + Str.hashCode() );
        char a_ ;
        a_ = 'a';
        int res ;
        res = 1+ a_
        System.out.println("1+a :" + res  );
    }
}

awk code

awk -f ./hashcode_test.awk

 hashcode_test.awk

BEGIN {
    for (ii = 0; ii < 256; ++ii) {
        ch = sprintf("%c", ii);
        ascii[ch] = ii;
    }
h = 0 ;
strings="www.runoob.com"
if(h ==0 && length(strings)>0)
{
  for (i=1;i<= length(strings)  ; ++i)
  {
      j=ascii[substr(strings,i,1)]
      print h " * 31 +" j |& "bc"
        "bc" |& getline var2
      #h=31*h+j
      h=var2
  } 
}
print "(" h " +2147483648)%4294967296-2147483648 "  |& "bc"
"bc" |& getline Result
print strings " , hashcode  " Result
}

实现结果

awk 结果

 java 结果

 oracle 函数实现  ，验证就不贴了

CREATE OR REPLACE FUNCTION HASHCODE(STR IN VARCHAR2) RETURN INTEGER IS
  RESULT INTEGER := 0;
BEGIN
  FOR I IN 1 .. LENGTH(STR) LOOP
    RESULT := 31 * RESULT + ASCII(SUBSTR(STR, I, 1));
  END LOOP;
  RESULT := MOD((RESULT + 2147483648), 4294967296) - 2147483648;
  RETURN(RESULT);
END HASHCODE;

awk function

function hashcode(strings)
{
for (ii = 0; ii < 256; ++ii) {
        ch = sprintf("%c", ii);
        ascii[ch] = ii;
    }
h = 0 ;
if(h ==0 && length(strings)>0)
{
  for (i=1;i<= length(strings)  ; ++i)
  {
      j=ascii[substr(strings,i,1)]
      print h " * 31 +" j |& "bc"
        "bc" |& getline var2
      h=var2
      #print i","substr(strings,i,1) " , " j" , " h
  } 
}
print "(" h " +2147483648)%4294967296-2147483648 "  |& "bc"
"bc" |& getline Result
#print strings " , hashcode  " Result
return Result
}
## test hashcode
BEGIN {
  a ="www.runoob.com"
  Hcode=  hashcode(a)
  print a " , hashcode  " Hcode
}