如何获得一系列字符？ （字母）

Question

I have been working on this for hours and now Im kinda stuck....please help me. Im a complete programming handicap. All the methods work fine except the alphabet one.

It will receive two characters (either upper or lower case) and return a string composed of the range of char values given. Maintain the same case (upper or lower) that was passed in to the method. If an upper case and a lower case char (one of each) was passed to the method, convert the upper case char into lower case and use the lower case range. Note, the range will be inclusive of the starting char and exclusive of the ending char. Also, observe that if the starting (first) char given is greater than the ending (second) char, for example 'm' and 'h', then the method will return an empty string since there are no chars in this range.

Can you give me some help on how I can do the above on the alphabet method?

import java.util.*;

class CharacterOperations
{
public static void run()
{
int number=1;
Scanner scanner = new Scanner(System.in);
while(number > 0)
{
System.out.println("(1) Insert 1 to change a letter from its lower case value to its upper case value");
System.out.println("(2) Insert 2 to change a letter from its upper case value to its lower case value ");
System.out.println("(3) Insert 3 for the alphabet method (range of two letters) ");
System.out.println("Enter a number (or negative to quit): ");
number = scanner.nextInt();

if (number == 1)
{
System.out.print("Enter a lower case letter: ");
String a= scanner.next();
char letter = (char) a.charAt(0);
toUpper(letter);
}
else if (number == 2)
{
System.out.print("Enter an upper case letter: ");
String a= scanner.next();
char letter = (char) a.charAt(0);
toLower(letter);
}
else if (number == 3)
{
System.out.print("Enter an upper case or lower case letter: ");
System.out.print("Enter an upper case or lower case letter: ");
String a= scanner.next();
char letter1 = (char) a.charAt(0);
String b= scanner.next();
char letter2 = (char) b.charAt(0);
alphabet(letter1, letter2);
}
}
}

public static char toUpper(char letter)
{
int rep = ((int)letter - 32);
char ltr = (char)rep;
System.out.println("The letter "+ ltr + " integer representation is: " + rep);
return (char) ((int) letter -32);
}

public static char toLower(char letter)
{
int rep = (int)(letter + 32);
char ltr = (char)rep;
System.out.println("The letter " + ltr + " integer representation is: " + rep);
return (char) ((int) letter + 32);
}

public static String alphabet( char letter1, char letter2){ 
 int rep1 = (int)letter1;
 int rep2 = (int)letter2;
 char ltr1 = (char)rep1;
 char ltr2 = (char)rep2;
System.out.println("The letter " + ltr1 + " integer representation is: " + rep1);
System.out.println("The letter " + ltr2 + " integer representation is: " + rep2);

}
}

Thanks!

Answer 1

for (char c = 'a'; c <= 'z'; c++) {
        System.out.println(c);
    }

it's very simple ^_^

Answer 2

With a char you can just ++ it to get the next char and so on.

char a = 'a';
a++; // now you have b
a++; // now you have c

Just do a while loop to go from start to end char.

Answer 3

Use this to first to generate a random letter. You first have to generate a random number within a certain range. Then when you get the number back and store it in a char variable, it shows it as a letter.

char letter = 0;
letter = (char) (65 + (char)(Math.random() * (90 - 65) + 1));

Answer 4

This answaer assumes you are just talking about standard keyboard characters from the ASCII set.

Take the ascii codes for the 2 charaters and create a loop:

StringBuilder buf = new StringBuilder();

for (int i = rep1; i <= rep2; ++i) 
    buf.append((char)i);

return buf.toString();

This will work as they both need to be same case...

Answer 5

public static String alphabet(char letter1, char letter2) { 
    StringBuffer out = new StringBuffer();    
    for (char c = letter1; c < letter2; c++) {
        out.append(c);
    }
    return out.toString();
}

Obviously you should add some error checking and handling

Answer 6

Simple solution:

    String str = "A"
    char cr = str.charAt(0);
    
    System.out.println((cr += 1)); //got B

Answer 7

public static String alphabet( char letter1, char letter2){

expects to return a String because you said public static "String"

take out the String and this should work, replace it by void if you just want to print with System.out.print. or return the string that your making

beside that my advise for going to uppercase and lowercase would have been to convert the char to a String and just use the java built in method.