Java方法总结与源码解析（未完待续）

使用StringTokenizer去掉字符串中的空格

public class StringTo {
    public static void main(String[] args){
        String text = " We are students ";
        System.out.println("源字符串是：");
        System.out.println(text);
        System.out.println(text.trim());
        StringTokenizer st = new StringTokenizer(text," ");
        StringBuffer sb = new StringBuffer();
        int i = 1;
        while(st.hasMoreTokens()){
            i++;
            sb.append(st.nextToken());
        }
        System.out.println("去掉字符串中所有空格之后的字符串是：");
        System.out.println(sb.toString());
    }
}

主要是通过st.hasMoreTokens实现的去除空格，那么我们观察下源码：

public StringTokenizer(String str, String delim, boolean returnDelims) {
  currentPosition = 0;
  newPosition = -1;
  delimsChanged = false;
  this.str = str;
  maxPosition = str.length();
  delimiters = delim;
  retDelims = returnDelims;
  setMaxDelimCodePoint();
  }

  public boolean hasMoreTokens() {
        /*
         * Temporarily store this position and use it in the following
         * nextToken() method only if the delimiters haven‘t been changed in
         * that nextToken() invocation.
         */
        newPosition = skipDelimiters(currentPosition);
        return (newPosition < maxPosition);
    }

 private int skipDelimiters(int startPos) {
        if (delimiters == null)
            throw new NullPointerException();

        int position = startPos;
        while (!retDelims && position < maxPosition) {
            if (!hasSurrogates) {
                char c = str.charAt(position);
                if ((c > maxDelimCodePoint) || (delimiters.indexOf(c) < 0))
                    break;
                position++;
            } else {
                int c = str.codePointAt(position);
                if ((c > maxDelimCodePoint) || !isDelimiter(c)) {
                    break;
                }
                position += Character.charCount(c);
            }
        }
        return position;
    }

public String nextToken() {
/*
* If next position already computed in hasMoreElements() and
* delimiters have changed between the computation and this invocation,
* then use the computed value.
*/

currentPosition = (newPosition >= 0 && !delimsChanged) ?
newPosition : skipDelimiters(currentPosition);

/* Reset these anyway */
delimsChanged = false;
newPosition = -1;

if (currentPosition >= maxPosition)
throw new NoSuchElementException();
int start = currentPosition;
currentPosition = scanToken(currentPosition);
return str.substring(start, currentPosition);
}

源码通过获取字符串的长度，遍历每个字符，将传入的字符进行比较，如果与需要截取的字符相同，则调用substring方法。