How to determine whether a string is an int in java
Nov 28, 2019 am 09:59 AM
1. Use the functions that come with JAVA
public static boolean isNumeric(String str){
for (int i = 0; i < str.length(); i++){
System.out.println(str.charAt(i));
if (!Character.isDigit(str.charAt(i))){
return false;
}
}
return true;
}Recommended related video tutorials: java teaching video
2. Use regular expressions
First, import java.util.regex.Pattern and java.util.regex. Matcher
public boolean isNumeric(String str){
Pattern pattern = Pattern.compile("[0-9]*");
Matcher isNum = pattern.matcher(str);
if( !isNum.matches() ){
return false;
}
return true;
}The first method can only verify numbers without the negative sign "-", that is, if you enter a negative number -199, the output result will be false; while the second method can be modified Regular expressions can be used to check negative numbers. Just change the regular expression to "^-?[0-9]" and change it to "-?[0-9].?[0-9]" to match all numbers. .
If you want to learn more related tutorials, you can visit: java introductory programming
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