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Java方法总结与源码解析(未完待续)

时间:2016-04-24 00:49:22      阅读:286      评论:0      收藏:0      [点我收藏+]

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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。

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Java方法总结与源码解析(未完待续)

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原文地址:http://www.cnblogs.com/yangsy0915/p/5426049.html

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