CODEWITHSUNDEEP
javastring
Nicole Havin
Nicole Havin

Reputation: 147

How to convert a string to uppercase without using the toUpperCase method?

I'm a beginner at java and can't get this code to work. What I have to do is convert any inputted string to uppercase without using the toUpperCase string method. This is what I have:

public String toUpperCase(String str)
{
    for(int i = 0; i < str.length(); i++)
    {
        char a = str.charAt(i);
        a = Character.toUpperCase(a);
        str += Character.toString(a);
    }
return str;
}

Upvotes: 7

Views: 13250

Answers (7)

Alex
Alex

Reputation: 1

public String toUpper(String str){

String strUp = "";
for(int i = 0; i<str.length(); i++) {
    char a = str.charAt(i);
    strUp += Character.toUpperCase(a);
}
return strUp;
}

Upvotes: -2

Jacob G.
Jacob G.

Reputation: 29680

C'mon guys, Java 8 has been out for years!

/**
 * Converts an all-lowercase String to
 * uppercase. Retains only spaces, any
 * other characters will be lost.
 */
public static String toUpperCase(String s) {
    int diff = 'a' - 'A'; // 32

    return s.chars()
            .filter(c -> c >= 'a' && c <= 'z' || c == ' ')
            .mapToObj(c -> String.valueOf((char) (c - (diff))))
            .collect(Collectors.joining());
}

Upvotes: 2

D.Kastier
D.Kastier

Reputation: 3015

There is the following way, but it doesn't consider any characters outside of English (no diacritics, no other language’s characters behind a-z).

public String toUpperCase(String str) {
    char[] chars = str.toCharArray();

    for (int i=0; i<chars.length; i++) {
        char c = chars[i];
        if ('a' <= c && c <= 'z') {
            chars[i] = (char) (c - 'a' + 'A');
        }
    }

    return new String(chars);
}

Upvotes: 6

toto
toto

Reputation: 1190

try it:

public static String toUpperCase(String str) {
        String result = "";
        for (int i = 0; i < str.length(); i++) {
            int v = str.charAt(i);
            if (v > 96 && v < 123) {
                v -= 32;
            }
            result+=(char)v;

        }
        return result;
    }

Upvotes: 1

κροκς
κροκς

Reputation: 590

Since you can't use the toUpperCase() method, you can use the ASCII table to get from a lower case letter to an upper case letter by subtracting 32.

'a' = 97, 'A' = 65
'b' = 98, 'B' = 66
...
'z' = 122, 'Z' = 90

public static int DIFF = 'a' - 'A'; // 32

public static String toUpperCase(String str) {
    StringBuilder sb = new StringBuilder();
    for (char c : str.toCharArray()) {
        if (Character.isLowerCase(c)) {
            sb.append(String.valueOf((char)(c - DIFF)));
        } else {
            sb.append(c);
        }
    }
    return sb.toString();
}

Upvotes: 1

user3437460
user3437460

Reputation: 17454

I am aware your school probably do not allow you to use StringBuilder and in case you can't use array as well. This is another primitive approach which your school may accept:

public static String toUpperCase(String s){
    String str = "";
    for(int x=0; x<s.length(); x++){
        char ch = s.charAt(x);
        if(ch >= 'a' && ch <= 'z')
            str += "" + (char)(ch - 32);
        else
            str += "" + ch; 
    }
    return str;
}

Test:

System.out.println(toUpperCase("aAbBcC"));

Output:

AABBCC

Upvotes: 2

Elliott Frisch
Elliott Frisch

Reputation: 201399

You are using str as input, and output (so your String has infinite length, as you keep adding characters). And you can use static, because you aren't using instance state. And, you might use a for-each loop. Finally, add another String, or better a StringBuilder like

public static String toUpperCase(String str) {
    StringBuilder sb = new StringBuilder();
    for (char ch : str.toCharArray()) {
        sb.append(Character.toUpperCase(ch));
    }
    return sb.toString();
}

Upvotes: 9

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