In the following example, two ways to change the first letter to uppercase will be shared.
Example 1
* Use ASCII table * The ASCII code of lowercase letters a-z is: 97-122;
public static String upperCaseFirstLetterV2(String str) {
if(str == null || str.length() <= 0) {
return str;
}
char[] cs = str.toCharArray();
if(cs[0] < 97 || cs[0] > 122) {
return str;
}
cs[0] -= 32;
return String.valueOf(cs);
}
Example 2
* Use string substring function and toUpperCase function
public static String upperCaseFirstLetterV1(String str) {
if(str == null || str.length() <= 0) {
return str;
}
String firstLetter = str.substring(0, 1);
if(!firstLetter.matches("[a-z]")) {
return str;
}
str = firstLetter.toUpperCase() + str.substring(1);
return str;
}
Sample code
public class UpperCase {
/**
* Use string substring function and toUpperCase function
*
* @param str
* @return
*/
public static String upperCaseFirstLetterV1(String str) {
if(str == null || str.length() <= 0) {
return str;
}
String firstLetter = str.substring(0, 1);
if(!firstLetter.matches("[a-z]")) {
return str;
}
str = firstLetter.toUpperCase() + str.substring(1);
return str;
}
/**
* Use ASCII table
* The ASCII code of lowercase letters a-z is: 97-122;
*
* @param str
* @return
*/
public static String upperCaseFirstLetterV2(String str) {
if(str == null || str.length() <= 0) {
return str;
}
char[] cs = str.toCharArray();
if(cs[0] < 97 || cs[0] > 122) {
return str;
}
cs[0] -= 32;
return String.valueOf(cs);
}
public static void main(String[] args) {
String str = "hello";
String s = upperCaseFirstLetterV1(str);
System.out.println("s = " + s);
String s1 = upperCaseFirstLetterV2(str);
System.out.println("s1 = " + s1);
}
}