令牌 - 字符串 Java

Question

我成功完成了以下任务，但是代码效率非常低，如果有人能告诉我一个更有效的方法，我将不胜感激，也许使用子字符串。作业：

/**
 * Separates a given string into tokens, which are the "words" that are
 * separated by one or more occurrences of the given separator character.
 * Returns the tokens as an array of String values.
 */
public static String[] tokenize (String str, char separator) {
    // Removes all the occurrences of the separator at the beginning and end of str
    String source = trim(str, separator);
    String[] tokens = new String[charRunCount (source,separator)+1];
    String tmp = ""; // a string in order to take a word, then run over this string
    int j = 0;
    int i = 0;
    while (i < tokens.length) {
        if ( source.charAt (j) != separator ) {
            do {
                tmp += source.charAt (j);
                if ( j >= source.length () - 1 ) {
                    break;
                }
                else { // so that we math the source length
                    j++;
                }
            } while (source.charAt (j) != separator); 
        }
        if ( source.charAt (j) == separator ) {
            j++;
            while (source.charAt (j) == separator) {
                j++;
            }
        }
        tokens[i] = tmp;// taking the token into place
        tmp = ""; //resetting the token so we can begin anew

        i++;
    }
    return tokens;
}

cahrRunCount 函数：

    public static int charRunCount(String str, char c){
    char last = 0;
    int counter = 0;
    for (int i = 0; i < str.length(); i++) {
        // whenever a run starts.
        if (last != c && str.charAt(i) == c) {
            counter++;
        }
        last = str.charAt(i);
    }
    return counter;
}

我不能使用 import 或 regex，谢谢！

Answer 1

使用 String.split 方法

String[] tokens = str.split(separator)


for(String token:tokens){
//your code goes here
}

文档在这里

https://docs.oracle.com/javase/7/docs/api/java/lang/String.html#split(java.lang.String)

Answer 2

如果需要，可以使用 String 类的 split 方法（就像@Amidala Siva Kumar 建议的那样），像这样：

public static String[] tokenize (String str, char separator) {
    String[] tokens = str.split(separator);
    return tokens;
}

或者，如果您想使用自己的拆分来执行此操作，您可以这样做（对您的代码的改进）。

public static String[] tokenize (String str, char separator) {
    String sep = ""+separator;
    int max_size = str.length() - str.replace(sep, "").length() +1 ; // Calculate max array size
    String[] temp = new String[max_size];
    int start = 0, index = 0, exact_size = 0;
    int pos = str.indexOf(separator);
    while (pos>=start) {
        if (pos>start){
            temp[index++] = str.substring(start,pos).trim();
            exact_size++;
        }
        start = pos + 1;
        pos = str.indexOf(separator,start); 
    }
    String[] tokens = new String[exact_size];
    System.arraycopy(temp, 0, tokens, 0, exact_size); 
    return tokens;
}

希望你觉得它有用。