How do I check if a Java String contains at least one capital letter, lowercase letter, and number?
For a simple string check, a single sweep through the string is enough. Since Regex will not offer any significant benefit, here is a simple for loop to achieve the same :
private static boolean checkString(String str) {
char ch;
boolean capitalFlag = false;
boolean lowerCaseFlag = false;
boolean numberFlag = false;
for(int i=0;i < str.length();i++) {
ch = str.charAt(i);
if( Character.isDigit(ch)) {
numberFlag = true;
}
else if (Character.isUpperCase(ch)) {
capitalFlag = true;
} else if (Character.isLowerCase(ch)) {
lowerCaseFlag = true;
}
if(numberFlag && capitalFlag && lowerCaseFlag)
return true;
}
return false;
}
Test run:
System.out.println(checkString("aBCd1")); // output is true
System.out.println(checkString("abcd")); //output is false
I think this should help OP's particular problem.
Example of @goshDeveloper's answer.
First create a Pattern variable with regular expression you want.
public final Pattern textPattern = Pattern.compile("^(?=.*[a-z])(?=.*[A-Z])(?=.*\\d).+$");
Second you can use it like this:
public boolean isTextValid(String textToCheck) {
return textPattern.matcher(textToCheck).matches();
}
Try regular expression
^(?=.*[a-z])(?=.*[A-Z])(?=.*\d).+$
descriptions are as follow
(?=.*[a-z]) -- check lower case letter
(?=.*[A-Z]) -- check upper case letter
(?=.*\d) -- check one digit exists