排序列表的分配

Question

My chapter 16 assignment is this.

Create an application which

• accepts user input of a string or words
• prints each word back in alphabetical order
• prints the total number of elements typed

I have this so far

import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;



public class Chapter16Assignment {
        public static void main(String[] args){

            Scanner input = new Scanner(System.in);


            String userInput = "";
            System.out.print(" Enter a line of words: ");
            userInput = input.nextLine();
            List<String> userString = Arrays.asList(userInput);
            String[]userInput
            //userString.add(userInput);
            //.split
            Collections.sort(userString);
            System.out.println(userString);
            //System.out.println("Frequency of words: " + Collection.frequency(userString));

            }



    }

I need to use split or something. i thought i could use sort method and frequency for part 3.

I expect the output to be enter a line of words then for it to print those words in alphabetical order, then the amount of words. at the moment its not doing any of that. its getting the users input though.

Answer 1

This is how you can use split method to convert string to string array. I am not using list since I want to show you a slightly different approach to do this problem.

I am removing white spaces and converting everything to lower case. It is up to you if you want to do it.

Scanner input = new Scanner(System.in);
String userInput;
System.out.print("Enter a line of words: ");
userInput = input.nextLine().replace(" ", "").toLowerCase();
String[] userInputSplit = userInput.split(""); // Splits array
Arrays.sort(userInputSplit); // Sorts array
System.out.println(Arrays.toString(userInputSplit)); // Prints sorted array
// Checks for frequency of each letter using maps
Map<String, Integer> countMap = Arrays.stream(userInputSplit)
        .collect(Collectors.toMap(Function.identity(), v -> 1, Integer::sum));
// Prints map
System.out.println("Frequency of words: " + countMap.toString());

Output:

Enter a line of words: The quick brown fox jumps over the lazy dog
[a, b, c, d, e, e, e, f, g, h, h, i, j, k, l, m, n, o, o, o, o, p, q, r, r, s, t, t, u, u, v, w, x, y, z]
Frequency of words: {a=1, b=1, c=1, d=1, e=3, f=1, g=1, h=2, i=1, j=1, k=1, l=1, m=1, n=1, o=4, p=1, q=1, r=2, s=1, t=2, u=2, v=1, w=1, x=1, y=1, z=1}

---

Edit:

Like @AndyTurner Suggested You can use Collectors.counting() as well which makes the syntax a bit easier to understand but it will return Long instead of Integer

Map<String, Long> countMap = Arrays.stream(userInputSplit)
                .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));

Collectors.counting is essentially

Map<String, Integer> countMap = Arrays.stream(userInputSplit)
        .collect(Collectors.toMap(Function.identity(), v -> 1L, Long::sum));

Using HashSet and Collections.frequency:

HashSet<String> uniqueValues = new HashSet<String>(userInputList);
for (String value : uniqueValues) {
    System.out.println("Frequency of " + value + " is: " + Collections.frequency(userInputList, value));
}