Several ways to determine whether it is an integer in java

方法一：用JAVA自带的函数

public static boolean isNumeric(String str){  
  for (int i = str.length();--i>=0;){    
   if (!Character.isDigit(str.charAt(i))){  
    return false;  
   }  
  }  
  return true;  
}

方法二：

/* 
  * 判断是否为整数  
  * @param str 传入的字符串  
  * @return 是整数返回true,否则返回false  
*/  
  
  
  public static boolean isInteger(String str) {    
    Pattern pattern = Pattern.compile("^[-\\+]?[\\d]*$");    
    return pattern.matcher(str).matches();    
  }

方法三：

public static boolean isNumeric(String str){  
    Pattern pattern = Pattern.compile("[0-9]*");  
    return pattern.matcher(str).matches();     
}

方法四：

public final static boolean isNumeric(String s) {  
        if (s != null && !"".equals(s.trim()))  
            return s.matches("^[0-9]*$");  
        else  
            return false;  
    }

方法五：用ascii码

public static boolean isNumeric(String str){  
   for(int i=str.length();--i>=0;){  
      int chr=str.charAt(i);  
      if(chr<48 || chr>57)  
         return false;  
   }  
   return true;  
}

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