Check out example codes for "java letter alphabet index". It will help you in understanding the concepts better.

Code Example 1

String str = "abcdef";
char[] ch  = str.toCharArray();
for(char c : ch){
    int temp = (int)c;
    int temp_integer = 96; //for lower case
    if(temp<=122 & temp>=97)
        System.out.print(temp-temp_integer);
}

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