Java：计算String中字母的出现次数

I am trying to write a program that counts the occurrence of letters in a string. For example, if the user inputs "Java", it will display "j: 1 a: 2 v:1". However, there seems to be something wrong with my program, and when I input the word java this is what it shows "j: 0 a: 1 v: 0"I am trying to write a program that counts the