String的面试题

//去除首尾的空格
  private static String claerTrim(String str) {
    
    String st = "";
    int flag = 0;
    int first=0,last=str.length();
    
    for(int i=0;i<str.length();i++){
      char ch = str.charAt(i);
      if(ch == ' '){
        continue;
      }else{
        first = i;
        break;
      }
    }
    
    for(int i=str.length()-1;i>0;i--){
      char ch = str.charAt(i);
      if(ch == ' '){
        continue;
      }else{
        last = i;
        break;
      }
    }
    
    System.out.println(first);
    System.out.println(last);
    
    
     while(first<=last){
      char ch = str.charAt(first);
       st = st + ch + "";
       System.out.println(st);
       first++;
    }
    
    //System.out.println(st);
    return st;
  }
  
  //获取上传文件名  "D:\\20120512\\day12\\Demo1.java"。
  public static String getFileName2( String path ){
      return path.substring( path.lastIndexOf("\\") + 1 );
    }
  }
  
  // 求一个子串在整串中出现的次数

   public static int getCount( String src , String tag ){ 
      // 0. 定义索引变量和统计个数的变量
      int index = 0;
      int count = 0;     
      // 1. 写循环判断
      while ( ( index = src.indexOf(tag) ) != -1 )   // jackjava
      {
       // 2. 求字串
         System.out.println( src );
       src = src.substring( index + tag.length() );   // index 4 + 4 = 8
      System.out.print( src.length() + " : " + index + " :  " + tag.length() );
           // 3. 累加
       count++;
         }
         return count;
    }