Alternately display any text that is typed in the textbox
// in either Capital or lowercase depending on the original
// letter changed. For example: CoMpUtEr will convert to
// cOmPuTeR and vice versa.
Switch.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e )
String characters = (SecondTextField.getText()); //String to read the user input
int length = characters.length(); //change the string characters to length
for(int i = 0; i < length; i++) //to check the characters of string..
{
char character = characters.charAt(i);
if(Character.isUpperCase(character))
{
SecondTextField.setText("" + characters.toLowerCase());
}
else if(Character.isLowerCase(character))
{
SecondTextField.setText("" + characters.toUpperCase()); //problem is here, how can i track the character which i already change above, means lowerCase**
}
}}
});
setText is changing the text content to exactly what you give it, not appending it.
Convert the String from the field first, then apply it directly...
String value = "This Is A Test";
StringBuilder sb = new StringBuilder(value);
for (int index = 0; index < sb.length(); index++) {
char c = sb.charAt(index);
if (Character.isLowerCase(c)) {
sb.setCharAt(index, Character.toUpperCase(c));
} else {
sb.setCharAt(index, Character.toLowerCase(c));
}
}
SecondTextField.setText(sb.toString());
You don't have to track whether you've already changed the character from upper to lower. Your code is already doing that since it's basically:
1 for each character x:
2 if x is uppercase:
3 convert x to lowercase
4 else:
5 if x is lowercase:
6 convert x to uppercase.
The fact that you have that else in there (on line 4) means that a character that was initially uppercase will never be checked in the second if statement (on line 5).
Example, start with A. Because that's uppercase, it will be converted to lowercase on line
3 and then you'll go back up to line 1 for the next character.
If you start with z, the if on line 2 will send you directly to line 5 where it will be converted to uppercase. Anything that's neither upper nor lowercase will fail both if statements and therefore remain untouched.
You can use StringUtils.swapCase() from org.apache.commons
This is a better method :-
void main()throws IOException
{
System.out.println("Enter sentence");
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
String str = br.readLine();
String sentence = "";
for(int i=0;i<str.length();i++)
{
if(Character.isUpperCase(str.charAt(i))==true)
{
char ch2= (char)(str.charAt(i)+32);
sentence = sentence + ch2;
}
else if(Character.isLowerCase(str.charAt(i))==true)
{
char ch2= (char)(str.charAt(i)-32);
sentence = sentence + ch2;
}
else
sentence= sentence + str.charAt(i);
}
System.out.println(sentence);
}
The problem is that you are trying to set the value of SecondTextField after checking every single character in the original string. You should do the conversion "on the side", one character at a time, and only then set the result into the SecondTextField.
As you go through the original string, start composing the output from an empty string. Keep appending the character in the opposite case until you run out of characters. Once the output is ready, set it into SecondTextField.
You can make an output a String, set it to an empty string "", and append characters to it as you go. This will work, but that is an inefficient approach. A better approach would be using a StringBuilder class, which lets you change the string without throwing away the whole thing.
String name = "Vikash";
String upperCase = name.toUpperCase();
String lowerCase = name.toLowerCase();
This is a better approach without using any String function.
public static String ReverseCases(String str) {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < str.length(); i++) {
char temp;
if (str.charAt(i) >= 'a' && str.charAt(i) <= 'z') {
temp = (char)(str.charAt(i) - 32);
}
else if (str.charAt(i) >= 'A' && str.charAt(i) <= 'Z'){
temp = (char)(str.charAt(i) + 32);
}
else {
temp = str.charAt(i);
}
sb.append(temp);
}
return sb.toString();
}
Here you are some other version:
public class Palindrom {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("Enter a word to check: ");
String checkWord = sc.nextLine();
System.out.println(isPalindrome(checkWord));
sc.close();
}
public static boolean isPalindrome(String str) {
StringBuilder secondSB = new StringBuilder();
StringBuilder sb = new StringBuilder();
sb.append(str);
for(int i = 0; i<sb.length();i++){
char c = sb.charAt(i);
if(Character.isUpperCase(c)){
sb.setCharAt(i, Character.toLowerCase(c));
}
}
secondSB.append(sb);
return sb.toString().equals(secondSB.reverse().toString());
}
}
StringBuilder b = new StringBuilder();
Scanner s = new Scanner(System.in);
String n = s.nextLine();
for(int i = 0; i < n.length(); i++) {
char c = n.charAt(i);
if(Character.isLowerCase(c) == true) {
b.append(String.valueOf(c).toUpperCase());
}
else {
b.append(String.valueOf(c).toLowerCase());
}
}
System.out.println(b);
Methods description:
*toLowerCase()* Returns a new string with all characters converted to lowercase.
*toUpperCase()* Returns a new string with all characters converted to uppercase.
For example:
"Welcome".toLowerCase() returns a new string, welcome
"Welcome".toUpperCase() returns a new string, WELCOME
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
String satr=scanner.nextLine();
String newString = "";
for (int i = 0; i < satr.length(); i++) {
if (Character.isUpperCase(satr.charAt(i))) {
newString+=Character.toLowerCase(satr.charAt(i));
}else newString += Character.toUpperCase(satr.charAt(i));
}
System.out.println(newString);
}
public class Toggle {
public static String toggle(String s) {
char[] ch = s.toCharArray();
for (int i = 0; i < s.length(); i++) {
char charat = ch[i];
if (Character.isUpperCase(charat)) {
charat = Character.toLowerCase(charat);
} else
charat = Character.toUpperCase(charat);
System.out.print(charat);
}
return s;
}
public static void main(String[] args) {
toggle("DivYa");
}
}
import java.util.Scanner;
class TestClass {
public static void main(String args[]) throws Exception {
Scanner s = new Scanner(System.in);
String str = s.nextLine();
char[] ch = str.toCharArray();
for (int i = 0; i < ch.length; i++) {
if (Character.isUpperCase(ch[i])) {
ch[i] = Character.toLowerCase(ch[i]);
} else {
ch[i] = Character.toUpperCase(ch[i]);
}
}
System.out.println(ch);
}
}
//This is to convert a letter from upper case to lower case
import java.util.Scanner;
public class ChangeCase {
public static void main(String[]args) {
String input;
Scanner sc= new Scanner(System.in);
System.out.println("Enter Letter from upper case");
input=sc.next();
String result;
result= input.toLowerCase();
System.out.println(result);
}
}
String str1,str2;
Scanner S=new Scanner(System.in);
str1=S.nextLine();
System.out.println(str1);
str2=S.nextLine();
str1=str1.concat(str2);
System.out.println(str1.toLowerCase());
来源：https://stackoverflow.com/questions/14972032/how-to-convert-lower-case-letters-to-upper-case-letters-and-upper-case-letters