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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