Write a program asking the user to enter letters from a$-$z or A$-$Z$.$ If the user enters a letter more than once, the letter will be stored in the array only one time. Repeated inputs will be filtered out. If the user enters anything other than the valid letters, the user must be prompted again. The program keeps asking the user until the array is filled with unique letters. Once the array is filled with the unique letters, the letters will be displayed all in uppercase letters. in java