Anyone tell me how java create hashcode internally ?
package swain.javainterviewhub.blogspot.in;
public class JavaInterviewHub {
public static void main(String[] args) {
String str="Alex";
System.out.println(str.hashCode());
}
}
Output:2043454
Key Hashcode Algorithm Hashcode
Alex A(1) + L(12) + E(5) + X(24)=42
From the documentation:
The hash code for a String object is computed as
s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]
You can also look at the source for additional information (Oracle JDK 8u45 here).
public int hashCode() {
int h = hash;
if (h == 0 && value.length > 0) {
char val[] = value;
for (int i = 0; i < value.length; i++) {
h = 31 * h + val[i];
}
hash = h;
}
return h;
}
Hash code generation in Java depends on the type of the object in question. For Strings, the algorithm is described in the Java docs (here).
Returns a hash code for this string. The hash code for a String object is computed as
s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]
using int arithmetic, where s[i] is the ith character of the string, n is the length of the string, and ^ indicates exponentiation. (The hash value of the empty string is zero.)
