Method 1: Use JAVA’s own function
public static boolean isNumeric(String str){
for (int i = str.length();--i>=0;){
if (!Character.isDigit(str.charAt(i ))){
return false;
}
}
return true;
}
Method 1 traverses each character of the string and uses the Character.isDigit() function to check whether each character is a number. If all characters in the string are numbers, this method will return true . However, if the string contains non-numeric characters, it will immediately return false .
This approach is neat and tidy, but may be overly strict because it considers a string like "123" (which contains a space at the end) not to be a number.
Method 2:
/*
* Determine whether it is an integer
* @param str The string passed in
* @return is an integer and returns true, otherwise it returns false
*/
public static boolean isInteger(String str) {
Pattern pattern = Pattern.compile("^ [-\+]?[\d]*$");
return pattern.matcher(str).matches();
}
Method 2 uses regular expressions to check whether the string contains only numbers. It matches all strings starting with the regular expression ["^[-+]?[\d]*$"] . This regular expression means that the beginning of the string can be a positive or negative sign, followed by any number of numbers. However, it thinks a string like "123" is an integer, when in fact "" is not part of a number.
Method three: FuncGPT (Hui function) automatically generates
package com.feisuanyz.function;
import com.feisuanyz.flow.core.cmpt.annotation.function.MethodDesc;
import com.feisuanyz.flow.core.cmpt.annotation.function.ParamDesc;
public class StringNumberChecker {
@MethodDesc (desc = " Determine whether the string is a number " ,
params = {
@ ParamDesc (name = "str" , desc = " String to be judged " ),
})
public static boolean isNumeric(String str) {
if (str == null || str . isEmpty ()) { // Check whether the string is empty
return false ;
}
try {
Double .parseDouble (str); // Use the Double.parseDouble() method to try to convert the string to double
return true ; // Conversion successful, the string is a number
} catch (NumberFormatException e) {
return false ; // Conversion failed, the string is not a number
}
}
}
Method three uses the Double.parseDouble() method to try to convert the string into a double-precision floating point number. If the conversion is successful, it means that the string is a number, and true is returned; if the conversion fails, it means that the string is not a number, and false is returned.
This code snippet includes an annotation @MethodDesc, which is used to describe some information about this method, including its description (desc) and parameters (params). The parameter description is also an array, where each element has a name (name) and description (desc). This kind of annotation is usually used to generate API documentation or for the code prompt function of some IDEs.
The design idea of this isNumeric method is reasonable and can meet the needs of most scenarios. However, it is important to note that since the Double.parseDouble() method can parse a string such as "3.14" into a valid floating point number, the method may be somewhat loose with the definition of "number" in the strict sense. If you need a more precise definition (for example, only accepting integer values or only floating point numbers with a specific number of decimal places), you may need to customize a more complex method to check the string.
Overall, this is a simple, clear way to efficiently check if a string can be parsed as a number.
方法四：
public final static boolean isNumeric(String s) {
if (s != null && !"".equals(s.trim()))
return s.matches("^[0-9]*$");
else
return false;
}
Method 4 first checks whether the string is empty or contains only spaces, and returns false if the condition is met . Then it uses String 's matches() method to check whether the string matches the regular expression "^[0-9]*$" . This regular expression means that the string consists only of numbers 0-9 . This method takes into account empty strings and spaces, but will still treat strings like "123" as numbers when encountered.
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;
}
This method determines whether it is a number by checking the ASCII code of each character in the string. If the character's ASCII code is not between 48 ( '0' ) and 57 ( '9' ), it immediately returns false . This method is very concise, but also very strict, and will consider a string like "123" not to be a number, even though " " is part of a number.
In summary, each of these methods has its advantages and disadvantages, and which method you choose depends on your specific needs and your definition of " numbers . "
FuncGPT is the latest feature launched by the full-stack automatic development tool SoFlu software robot. It focuses on AI- generated Java functions, describes Java function requirements through natural language, and generates high-quality, highly readable Java function codes in real time. The generated code can be directly copied to IDEA , or imported into the Java fully automatic development tool function library with one click. Now available for free development and use, link:https://suo.im/aWkTE
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