How to split string on the first white space in Salesforce

Consider the following string,

Input:

Only for Salesforce

I need to get the desired output like,

Output:

Only = String 1

For salesforce = String 2

If you want to split string on the first white space means consider the following method,

1. String str =’Only for Salesforce’;
2. String str1,str2;
3. 
   
4. str1=str.substring(0,str.indexOf(' '));
5. str2=str.substring(str.indexOf(' ')+1);
6. 
   
7. system.debug(‘String 1 ## ' + str1);  // returns Only
8. system.debug('String 2 ##' + str2);  // returns for Salesforce