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
– Sam I am says Reinstate Monica, Commented Nov 20, 2013 at 23:29

nanofarad · Accepted Answer · 2013-11-20 23:29:42Z

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, 2013 at 23:29

nanofarad

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3 Comments

Sam I am says Reinstate Monica Over a year ago

aren't you supposed to pass i into charAt?

nanofarad Over a year ago

@SamIam My oversight, fixed.

Dale22599 Over a year ago

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.

Jeroen Vannevel · Accepted Answer · 2013-11-20 23:32:41Z

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.

pobrelkey · Accepted Answer · 2013-11-20 23:32:28Z

0

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;
    }
}

answered Nov 20, 2013 at 23:32

pobrelkey

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