Java将错误的数据写入数组

Question

我正在实现算法，该算法将计算链接列表中唯一数字的出现次数。问题出在 for 循环中，当输入类似于 1 1 1 2 2 2

时，我正在计算出现次数

而不是获取输出

1 appearance 3 times
2 appearance 3 times

我懂了

1 appearance 3
0 appearance 0

使用输入1 2 3 4 5 6 7 8 9我得到了数组超出索引的异常。这是代码

public static void main(String[] args) {
    LinkedList<Integer> list = new LinkedList<Integer>();
    Scanner user_input = new Scanner(System.in);
    String input = user_input.nextLine();
    //Getting user input, if the user enter an empty line(enter, enter) the loop will die
    while(input.length() > 0){
        list.add(Integer.parseInt(input));
        input = user_input.nextLine();
    }
    Collections.sort(list); //sorting the input
    //Getting the number of unique numbers
    int count_of_unique_numbers = 1;// There will be atleast one unique number

    if(!list.isEmpty()){
        int temp = list.get(0);
        for(int i = 1;i < list.size(); i++){
            if(temp != list.get(i)){
                count_of_unique_numbers++;
                temp = list.get(i);
            }
        }
    }
    else{
        System.out.println("The list is empty"); 
        return;
    } 
    //Counting how many times the unique numbers apper;
    int number_appearance[][] = new int[count_of_unique_numbers][2];
    int temp = list.get(0);
    int counter = 1;
    int j = 0;
    for(int i = 1;i < list.size();i++){
        if(temp == list.get(i)){ counter++; }
        else{
            number_appearance[j][0] = temp;
            number_appearance[j][1] = counter;
            counter = 1;
            temp = list.get(i);
            j++;
        }
    }
    //Printing the number_appearance array
    for(int i = 0; i < count_of_unique_numbers; i++){
        System.out.println("The number: " + number_appearance[i][0] + " appearece " + number_appearance[i][1] + " times");
    }
}

Answer 1

您可以将所有这些简单地归结为这一点。

Map < String, Integer > numMap = new HashMap < String, Integer > ();
Scanner user_input = new Scanner(System. in );
String input = user_input.nextLine();

String[] inputArray = input.split(" ");
for (String s: inputArray) {
    if (numMap.containsKey(s)) {
        numMap.put(s, numMap.get(s) + 1);
    } else {
        numMap.put(s, 1);
    }
}

for (Map.Entry < String, Integer > entry: numMap.entrySet()) {
    System.out.println("number: " + entry.getKey() + " appeared: " + entry.getValue() + " times");
}