Java中s.charAt(index)用于提取字符串s中的特定字符操作

public class hash { 
 
 public static void main(String[] args) {
 // TODO Auto-generated method stub 
 
  String str = "This is yiibai"; 
  
  // prints character at 1st location
  System.out.println(str.charAt(0));  
  
  // prints character at 5th location i.e white-space character
  System.out.println(str.charAt(4));
  
  // prints character at 18th location
  System.out.println(str.charAt(6));
 }
}

    String str1="abdc686512ffsc1267d";
    String substr1=str1.substring(4);
    
    //指定区间（不包括结束索引处）
    String substr2=str1.substring(4, 10);
    System.out.println("substr1="+substr1);
    System.out.println("substr2="+substr2);
    System.out.println("*****************************");
    
    //结合使用indexOf()灵活截取示例
    String str2="<![CDATA[3-4级]]>";
    String cutstr=str2.substring(9, str2.indexOf("]]"));
    System.out.println("cutstr="+cutstr);

    System.out.println("正则表达式:");
    //正则表达式
    String str2="<![CDATA[3-4级]]>";
    String fengli="\\[CDATA\\[(.*?)\\]\\]>";//提取风级的正则表达式
    Pattern pafengli=Pattern.compile(fengli);
    Matcher matfengli = pafengli.matcher(str2);
    if(matfengli.find())
    {
     cutstr = matfengli.group(1); //group为捕获组
     System.out.println("cutstr="+cutstr);
    }
    else
     System.out.println("没找到");