How to replace a specific part of an ArrayList?

Question

So I have an ArrayList here:

story.add("Select the type of bread you want to use. Many prefer the taste of [Color] bread, while others prefer [Noun1] bread because it is healthy.");
story.add("Choose the flavor of Jam/Jelly. I personally prefer [Food] jam, but you can use whatever you want.");
story.add(" Choose the type of peanut butter - either [Adjective1] or [Adjective2].");
story.add("Take out [Number] slice(s) of bread.");
story.add(" Use a [Noun2] to [Verb1] the jam all over on of the pieces of bread.");
story.add(" Now [Verb2] the peanut butter on the other piece of bread.");
story.add("Put them together, and you have a PB&J [Verb3].");

I am trying to replace an individual part of the ArrayList . For example, I want to replace [Color] with an actual color without replacing the whole ArrayList . Is this possible?

Thanks.

Answer 1

Use a ListIterator , so you can replace the value while iterating:

for (ListIterator<String> iter = story.listIterator(); iter.hasNext(); ) {
    String line = iter.next();
    line = line.replace("[Color]", "BLUE");
    iter.set(line);
}

story.forEach(System.out::println);

Output

Select the type of bread you want to use. Many prefer the taste of BLUE bread, while others prefer [Noun1] bread because it is healthy.
Choose the flavor of Jam/Jelly. I personally prefer [Food] jam, but you can use whatever you want.
 Choose the type of peanut butter - either [Adjective1] or [Adjective2].
Take out [Number] slice(s) of bread.
 Use a [Noun2] to [Verb1] the jam all over on of the pieces of bread.
 Now [Verb2] the peanut butter on the other piece of bread.
Put them together, and you have a PB&J [Verb3].

If you want to replace many of the placeholders in a single iteration, then do it like this (Java 9+):

Map<String, String> map = new HashMap<>();
map.put("Color", "BLUE");
map.put("Adjective1", "SMOOTH");
map.put("Adjective2", "CHUNKY");
map.put("Number", "THREE");

Pattern p = Pattern.compile("\\[([^\\]]+)\\]");
for (ListIterator<String> iter = story.listIterator(); iter.hasNext(); ) {
    String line = iter.next();
    line = p.matcher(line).replaceAll(mr -> map.getOrDefault(mr.group(1), mr.group(0)));
    iter.set(line);
}

Output

Select the type of bread you want to use. Many prefer the taste of BLUE bread, while others prefer [Noun1] bread because it is healthy.
Choose the flavor of Jam/Jelly. I personally prefer [Food] jam, but you can use whatever you want.
 Choose the type of peanut butter - either SMOOTH or CHUNKY.
Take out THREE slice(s) of bread.
 Use a [Noun2] to [Verb1] the jam all over on of the pieces of bread.
 Now [Verb2] the peanut butter on the other piece of bread.
Put them together, and you have a PB&J [Verb3].

Answer 2

I am assuming this is an ArrayList of String 's like so:

ArrayList<String> story = new ArrayList<String>();
story.add("Select the type of bread you want to use. Many prefer the taste of [Color] bread, while others prefer [Noun1] bread because it is healthy.");
...

In this case, you need to replace the CharSequence [Color] with your new value:

story.get(0).replace("[Color]", "yellow");

If you want to overwrite the original ArrayList with the replaced value you would do...

story.set(0, story.get(0).replace("[Color]", "yellow"));

Answer 3

Well,you don't have to iterate over Array.It can also be done by using stream . You can change any value in the collection using one line of code with .stream() method.

    story.stream().map( n ->n.replace("VALUE_YOU_WANT_TO_REPLACE","VALUE_YOU_WANT_TO_BE_REPLACED")).collect(Collectors.toList());

For example if you want to replace "[Color]" with "Blue"

    story = (ArrayList<String>) story.stream().
        map(n ->n.replace("[Color]","BLUE")).collect(Collectors.toList());

Answer 4

You can do it in one short line...

Given a map of your desired values:

Map<String, String> map = Map.of("[Color]", "green", "[Food]", "fries"); // etc

This does the transform:

map.forEach((k, v) -> story.replaceAll(s -> s.replace(k, v)));

See javadoc for List#replaceAll

Note that this solution does not make use of regex matching.