JAVA checks whether a string is a number.

The following describes several methods to check whether a string is a number:
1. Use JAVA built-in functions
[Java]
Atic boolean isNumeric (String str ){
For (int I = str. length (); -- I> = 0 ;){
If (! Character. isDigit (str. charAt (I ))){
Return false;
}
}
Return true;
}
2. Regular Expression
[Java]
Public static boolean isNumeric (String str ){
Pattern pattern = Pattern. compile ("[0-9] *");
Return pattern. matcher (str). matches ();
}
3. Regular Expression
[Java]
Public static boolean isNumeric (String str ){
If (str. matches ("\ d *"){
Return true;
} Else {
Return false;
}
}
4. Use ascii code
[Java]
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;
}
Generally, the usage frequency may be 2 or 3. Of course, there are some other methods. Here we only list some of the methods with relatively high usage frequency.