词频计数器 - Java

Question

import java.io.EOFException;

public interface ICharacterReader {
char GetNextChar() throws EOFException;
void Dispose();
}

import java.io.EOFException;
import java.util.Random;

public class SimpleCharacterReader implements ICharacterReader {
private int m_Pos = 0;

public static final char lf = '\n';

private String m_Content = "It was the best of times, it was the worst of times," + 
lf +
"it was the age of wisdom, it was the age of foolishness," + 
lf +
"it was the epoch of belief, it was the epoch of incredulity," + 
lf +
"it was the season of Light, it was the season of Darkness," + 
lf +
"it was the spring of hope, it was the winter of despair," + 
lf +
"we had everything before us, we had nothing before us," + 
lf +
"countries it was clearer than crystal to the lords of the State" + 
lf +
"preserves of loaves and fishes, that things in general were" + 
lf +
"settled for ever";

Random m_Rnd = new Random();

public char GetNextChar() throws EOFException {

    if (m_Pos >= m_Content.length()) {
        throw new EOFException();
    }

    return m_Content.charAt(m_Pos++);

}

public void Dispose() {
    // do nothing
}
}

Basically I have created an interface called ICharacterReader that gets the next character in a sentence and throws an exception once there are no more characters. Underneath it I created a class called SimpleCharacterReader that includes a list of random sentences that need to be counted in a word frequency. However, now I am trying to make a separate class that takes the ICharacterReader interface as an argument and simply returns the word frequencies. I'm a beginner at programming so not really sure what to do here, any simple suggestion would be appreciated.

Answer 1

Your task can be done in two parts:

1. Reading the char data and combining it to a String

Just use a StringBuilder and append char s until you get a exception.

ICharacterReader reader = ...
StringBuilder sb = new StringBuilder();
try{
    while (true) {
        sb.append(reader.GetNextChar());
    }
} catch (EOFException ex) {
}
String stringData = sb.toString();

2. Counting word fequencies

Simply split the words using a regular expression and then simply count how often each word occurs. You can do this easily by using the Stream API:

Map<String, Long> frequencies = Arrays.stream(stringData.split(" +|\n"))
                                      .collect(Collectors.groupingBy(Function.identity(),
                                                                     Collectors.counting()));