Java method to determine whether string is a number

Method to determine whether a string is a number in java:

1. Use JAVA’s own function

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;
}

charAt() method for Returns the character at the specified index. The index range is from 0 to length() - 1.

Syntax

public char charAt(int index)

Parameters: index -- The index of the character.

Return value: Returns the character at the specified index.

isDigit() method is used to determine whether the specified character is a number.

Syntax: public static boolean isDigit(char ch)

Parameters: ch -- The character to be tested.

Return value: If the character is a number, return true; otherwise, return false.

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;
}

3. Use org .apache.commons.lang

org.apache.commons.lang.StringUtils;
boolean isNunicodeDigits=StringUtils.isNumeric("aaa123456789");

For more java knowledge, please pay attention to the java basic tutorial column.

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