使用整數添加數組索引

Question

我正在處理一個問題，我必須計算文本中字符的頻率。我沒有編碼，有點生疏，所以我認爲這將有助於我的代碼第二雙眼睛。 我的代碼在一個文件中讀取，理想情況下，它應該打我的if語句並將「1」添加到我的頻率數組中。但是，它總是打印「0」。我沒有正確添加？

public class hw4{ 
public static void main (String []args)throws IOException{ 

//ask user to enter file name 
System.out.printf("Enter a file location and name to encode [press Enter]: "); 

Scanner input = new Scanner(System.in); 
String filename = input.next(); 

//Gets file name from Scanner and checks to see if valid 
File file = new File(filename); 
Scanner text = new Scanner(file); 

String[] letters = {"a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"}; 
int[] freq = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}; 

String letter; 

    while(text.hasNext()){ 
     letter = text.next(); 

     if (letter == "a"){ 
     freq[0] = freq[0] + 1; 
     } 
     if (letter == "b"){ 
     freq[1] = freq[1] + 1; 
     } 
     if (letter == "c"){ 
     freq[2] = freq[2] + 1; 
     } 
     if (letter == "d"){ 
     freq[3] = freq[3] + 1; 
     } 
     if (letter == "e"){ 
     freq[4] = freq[4] + 1; 
     } 
     if (letter == "f"){ 
     freq[5] = freq[5] + 1; 
     } 
     if (letter == "g"){ 
     freq[6] = freq[6] + 1; 
     } 
     if (letter == "h"){ 
     freq[7] = freq[7] + 1; 
     } 
     if (letter == "i"){ 
     freq[8] = freq[8] + 1; 
     } 
     if (letter == "j"){ 
     freq[9] = freq[9] + 1; 
     } 
     if (letter == "k"){ 
     freq[10] = freq[10] + 1; 
     } 
     if (letter == "l"){ 
     freq[11] = freq[11] + 1; 
     } 
     if (letter == "m"){ 
     freq[12] = freq[12] + 1; 
     } 
     if (letter == "n"){ 
     freq[13] = freq[13] + 1; 
     } 
     if (letter == "o"){ 
     freq[14] = freq[14] + 1; 
     } 
     if (letter == "p"){ 
     freq[15] = freq[15] + 1; 
     } 
     if (letter == "q"){ 
     freq[16] = freq[16] + 1; 
     } 
     if (letter == "r"){ 
     freq[17] = freq[17] + 1; 
     } 
     if (letter == "s"){ 
     freq[18] = freq[18] + 1; 
     } 
     if (letter == "t"){ 
     freq[19] = freq[19] + 1; 
     } 
     if (letter == "u"){ 
     freq[20] = freq[20] + 1; 
     } 
     if (letter == "v"){ 
     freq[21] = freq[21] + 1; 
     } 
     if (letter == "w"){ 
     freq[22] = freq[22] + 1; 
     } 
     if (letter == "x"){ 
     freq[23] = freq[23] + 1; 
     } 
     if (letter == "y"){ 
     freq[24] = freq[24] + 1; 
     } 
     if (letter == "z"){ 
     freq[25] = freq[25] + 1; 
     } 
    } 

    for(int i=0; i <26; i++){ 
    System.out.printf("%s:%d\n", letters[i], freq[i]); 
    } 
} 

}

Answer 1

我意識到，有一個等效問題。

的檢查是不是

如果（==字母 「A」）

但

如果（letter.equals（ 「A」）