Java - Replacing many strings at once

Question

So I'm trying to write a program that takes a String (str) and converts it to NATO Phonetic Alphabet (newSentence).

This is what I tried:

newSentence = str.toLowerCase().replace("a", "Alpha ")
                               .replace("b", "Bravo ")
                               .replace("c", "Charlie ")
                               .replace("d", "Delta ")
                               .replace("e", "Echo ")
                               .replace("f", "Foxtrot ")
                               .replace("g", "Golf ")
                               .replace("h", "Hotel ")
                               .replace("i", "India ")
                               .replace("j", "Juliet ")
                               .replace("k", "Kilo ")
                               .replace("l", "Lima ")
                               .replace("m", "Mike ")
                               .replace("n", "November ")
                               .replace("o", "Oscar ")
                               .replace("p", "Papa ")
                               .replace("q", "Quebec ")
                               .replace("r", "Romeo ")
                               .replace("s", "Sierra ")
                               .replace("t", "Tango ")
                               .replace("u", "Uniform ")
                               .replace("v", "Victor ")
                               .replace("w", "Whiskey ")
                               .replace("x", "X-Ray ")
                               .replace("y", "Yankee ")
                               .replace("z", "Zulu ");

However, this obviously doesn't work since after it replaces every "a" with "Alpha," it'll take every "l" "p" and "h" and reconvert those and so on. Is there some way to convert all of the letters at once so that this doesn't happen, and make it much more efficient?

maybe instead of calling `replace` a bunch of times, you can iterate over each character and build a completely **new** string based upon your input string — Sam I am says Reinstate Monica, Nov 20 '13 at 23:29

score 2 · Accepted Answer · answered Nov 20 '13 at 23:29

2

Create a new string iteratively:

StringBuilder outSB = new StringBuilder();
for(int i=0; i < str.length(); i++){
    if(str.charAt(i) == 'a' || str.charAt(i) == 'A') outSB.append("Alpha ");
    if(str.charAt(i) == 'b' || str.charAt(i) == 'B') outSB.append("Bravo ");
    // and so on
}
String output = outSB.toString();

answered Nov 20 '13 at 23:29

nanofarad

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aren't you supposed to pass `i` into `charAt`? – Sam I am says Reinstate Monica Nov 20 '13 at 23:30
@SamIam My oversight, fixed. – nanofarad Nov 20 '13 at 23:31
Awesome, thanks, worked perfectly. The only thing I changed is I turned every `if` besides the first one to `else if` and at the end I added `else outSB.append(str.charAt(i) + " ");` for if it wasn't a letter. – Dale22599 Nov 20 '13 at 23:58

score 1 · Answer 2 · answered Nov 20 '13 at 23:32

private static Map<Character, String> lookup = new HashMap<>();
public static void main(String[] args) {
    String input = "abc";
    StringBuilder sb = new StringBuilder();

    for(char c : input.toCharArray()){
        sb.append(lookup.get(c));
        sb.append(" ");
    }

    System.out.println(sb.toString());

}

static {
    lookup.put('a', "Alpha");
    lookup.put('b', "Bravo");
    lookup.put('c', "Charlie");
}

Output:

Alpha Bravo Charlie

Create a lookup table and construct a new string based on each character in your original string.

score 0 · Answer 3 · answered Nov 20 '13 at 23:32

StringBuilder sb = new StringBuilder();
for (char c : str.toLowerCase().toCharArray()) {
    switch (c) {
        case 'a':  
            sb.append("Alpha ");
            break;
        case 'b':  
            sb.append("Bravo ");
            break;
        // and so on until Zulu...
        default:
            // optional: just pass through any character not in NATO alphabet
            sb.append(c);
            break;
    }
}

Java - Replacing many strings at once

3 Answers3