json串中包含英文逗号，引号，大于号，小于号的解决方法

public static String stringToJson(String s) {    
          StringBuffer sb = new StringBuffer ();     
          for (int i=0; i<(); i++) {     
        
              char c = (i);     
              switch (c) {     
              case '\"':     
                  ("\\\"");     
                  break;     
//              case '\\':   //如果不处理单引号，可以释放此段代码，若结合下面的方法处理单引号就必须注释掉该段代码
//                  ("\\\\");     
//                  break;     
              case '/':     
                  ("\\/");     
                  break;     
              case '\b':      //退格
                  ("\\b");     
                  break;     
              case '\f':      //走纸换页
                  ("\\f");     
                  break;     
              case '\n':     
                  ("\\n"); //换行    
                  break;     
              case '\r':      //回车
                  ("\\r");     
                  break;     
              case '\t':      //横向跳格
                  ("\\t");     
                  break;     
              default:     
                  (c);    
              }}
          return ();     
       }