Converting chars into a string (without array)?

Question

I need to convert a set of chars into a string. The problem is, I don't know how to do it without an array (it's forbidden to use them, because we didn't see the this subject yet).

So the method starts with asking the user to type in a word (String type). In this case I use the word "programma" as an example. The first step is too count +4 to every character of that word. In this example it must change from "programma" --> "tvskveqqe".

I split up the input string "programma", into seperate chars, and added +4 in the alfabet. Afterwards I made sure if the letters "wxyz" are used, that they are converted to w --> a, x -->b, y --> c and z --> d.

But now I'm stuck at the part, where I need to put the chars 't''v''s''k''v''e''q''q''e' into a string "tvskveqqe", and use that as return statement.

Thanks!

    public char coderen() {
    String str; //input string
    char c, e = ' ';
    int a = 4, b, d;

    System.out.println("Geef een woord in: "); 
    str = Input.readString(); //input

    for (int i = 0; i < str.length(); i++) { // Splits up the string into separate chars
        b = (int) str.charAt(i) + a; // +4 in ASCII
        c = (char) b;

        if (c >= 'e' && c <= 'z') {
            e = c;
            System.out.println(e);
        }
        else if (c >= '{' && c <= '~') { // converts 'w''x''y''z' into 'a''b''c''d'
            d = (int)c - 26;
            e = (char) d;
            System.out.println(e);
        }
        else {
            System.out.println("fout!");
        }
    }
    return e;
}

Use [`String.replace(char, char)`](https://docs.oracle.com/javase/8/docs/api/java/lang/String.html#replace-char-char-) — khelwood, Nov 10 '14 at 16:02
It would interesting to handle [ĳ](http://www.fileformat.info/info/unicode/char/0133/index.htm). — Tom Blodget, Nov 10 '14 at 17:46
Instead of working with if and else, you could calculate the correct character: int ascii = (int)str.charAt(i); int substituteAscii = (ascii - 97 + 4) % 27; //ASCII value of 'a' == 97 — Michaël Benjamin Saerens, Jan 06 '15 at 14:40

score 1 · Answer 1 · edited May 23 '17 at 11:57

You have various ways to do it.

There's String.concat() for example

String str = "";
str.concat(new String(myChar));

it's pratically the same as doing

str += mychar;

But generally its a bad practice because Strings are immutable, they consume memory and here you're creating a lot of them.

The best you can use is a StringBuilder:

StringBuilder builder = new StringBuilder();
builder.append(myChar1);
builder.append(myChar2);
...
builder.toString();

As a side note I would say that if you're using a String you are actually using a char array. String is a wrapper class for a char[] structure:

public final class String
    implements java.io.Serializable, Comparable<String>, CharSequence {
    /** The value is used for character storage. */
    private final char value[];
    ...

score 0 · Answer 2 · answered Nov 10 '14 at 16:04

Try this. You'll get the idea. It does not use any arrays.

public static void main(String[] args) throws Exception {
    char ch = 'a';
    String s = ch + "";
    for (int i=1; i<=10; i++){
        s += (char)(ch + i);
    }
    System.out.println(s);      
}

But now I'm stuck at the part, where I need to put the chars 't', 'v', 's', 'k', 'v', 'e', 'q', 'q', 'e' into a string "tvskveqqe", and use that as return statement.

You can use an ArrayList also (provided you are disallowed to use an array).
Then loop through it and do what I did above.

score 0 · Accepted Answer · answered Nov 10 '14 at 16:08

It's a bit strange that you should not use arrays as in the end a string is always represented as an array of characters, so you could argue that any approach that you apply is "using an array"...

Having said that, you could try different things:

Using a StringBuilder:

StringBuilder sb = new StringBuilder();
for .... { sb.appendChar(c); }

Using String concatenation:

String result = "";
for .... { result = result + c; }

Using String replace: (However this is not based on index but on matching characters):

for (char c = 'a'; c <= 'z'; c++) {
    result = result.Replace(c, c + 4);
}

Converting chars into a string (without array)?

3 Answers3