按字母顺序显示 ArrayList

Question

我写了一个 class，它接受一个字符串，计算字符串中每个字母的出现次数，然后打印每个字母的出现次数。我希望它按字母顺序显示，但不知道该怎么做。

import java.util.ArrayList; // import the ArrayList class

class CryptCmd {

    public static void CryptCmd(String str) {

        ArrayList<String> occurs = new ArrayList<>();

        final int MAX_CHAR = 256;

        // Create an array of size 256 i.e. ASCII_SIZE
        int[] count = new int[MAX_CHAR];

        int len = str.length();

        // Initialize count array index
        for (int i = 0; i < len; i++)
            count[str.charAt(i)]++;

        // Create an array of given String size
        char[] ch = new char[str.length()];
        for (int i = 0; i < len; i++) {
            ch[i] = str.charAt(i);
            int find = 0;
            for (int j = 0; j <= i; j++) {

                // If any matches found
                if (str.charAt(i) == ch[j])
                    find++;
            }

            if (find == 1)
                occurs.add("Number of Occurrence of " + str.charAt(i) + " is: " + count[str.charAt(i)] + "\n");
        }

        System.out.println(String.join("",occurs));

        int total = 0;
        for(int i = 0; i < str.length(); i++) {
            if(str.charAt(i) != ' ')
                total++;
        }
        System.out.println("Total chars is " + total);
    }
}

到目前为止，打印按照找到字母的顺序显示，即

"Hello" = 
Number of Occurrence of H is: 1
Number of Occurrence of e is: 1
Number of Occurrence of l is: 2
Number of Occurrence of o is: 1

Total chars is 5

所需的输出是这样的，按字母顺序排列，即

"Hello" =
Number of Occurrence of e is: 1
Number of Occurrence of H is: 1
Number of Occurrence of l is: 2
Number of Occurrence of o is: 1

Total chars is 5

Answer 1

它 returns 因为 H 在你的情况下是大写，而在 ASCII ordering 之前是小写字母。

A - 65 - 起始于

a - 97 - 开始于

就是这个原因。

维护一个案例就妥当了。否则你必须自己写 comparator order 类似于 this.

Answer 2

这是代码


import java.util.*; // import the ArrayList class


class CryptCmd1 {
    public static void main(String[] args) {
        CryptCmd("Hello");
    }
    public static void CryptCmd(String str) {

        ArrayList<String> occurs = new ArrayList<>();

        final int MAX_CHAR = 256;

        // Create an array of size 256 i.e. ASCII_SIZE
        int[] count = new int[MAX_CHAR];

        int len = str.length();

        // Initialize count array index
        for (int i = 0; i < len; i++)
            count[str.charAt(i)]++;

        // Create an array of given String size
        char[] ch = new char[str.length()];
        for (int i = 0; i < len; i++) {
            ch[i] = str.charAt(i);
            int find = 0;
            for (int j = 0; j <= i; j++) {

                // If any matches found
                if (str.charAt(i) == ch[j])
                    find++;
            }
            String outString = "Number of Occurrence of " + str.charAt(i) + " is: " + count[str.charAt(i)] + "\n";

            if (find == 1)
                occurs.add(outString.toLowerCase());
        }
        Collections.sort(occurs);
        System.out.println(String.join("",occurs));

        int total = 0;
        for(int i = 0; i < str.length(); i++) {
            if(str.charAt(i) != ' ')
                total++;
        }
        System.out.println("Total chars is " + total);
    }
}

我已经使用collectionsclass对数组进行排序并满足您的要求

Answer 3

打印之前只需添加以下排序逻辑

Collections.sort(occurs, (a,b) -> a.compareToIgnoreCase(b));

按字母顺序显示 ArrayList

Displaying an ArrayList alphabetically

java

arrays

arraylist

tostring