Java String replace with Regular expression with new pattern in Array

Java's string formatting has a built-in syntax for this. The general format is:

%[argument_index$][flags][width][.precision]conversion

so you can use e.g. %1$s to mean the first format parameter, %2s the second etc. Note that the indexes are one-based, not zero-based.

e.g.

String[] fruits = {"Banana", "Orange", "Apple", "Grape"};
System.out.format(
    "My most favorite fruit is %1$s, but I also like %2$s and %4$s",
    fruits);

Use String.replace

String sentence = "My most favorite fruit is [0], but I also like [1] and [3]";
String[] replacements = {"Banana", "Orange", "Apple", "Grape"};
for(int i = 0; i < replacements.length; i++)
    sentence = sentence.replace("[" + i + "]", replacements[i]);

If you are able to change the format of paragraph then you might start from this snippet.

String paragraph = "My most favorite fruit is %s, but I also like %s and %s";
String[] fruits = {"Banana", "Orange", "Apple", "Grape"};
System.out.printf(paragraph, fruits[0], fruits[1], fruits[2]);                 

output

My most favorite fruit is Banana, but I also like Orange and Apple

edit Another solution where don't have to maintain the positional parameters of the fruits could be.

String paragraph = "My most favorite fruit is {0}, but I also like {1} and {3}";
Object[] fruits = {"Banana", "Orange", "Apple", "Grape"};
MessageFormat mf = new MessageFormat(paragraph);
System.out.println(mf.format(fruits));

output

My most favorite fruit is Banana, but I also like Orange and Grape

You can use the following code (see demo):

ArrayList<String> fruits_arr = new ArrayList<String>(); // Just initializing the array
        fruits_arr.add("Banana");        
        fruits_arr.add("Orange");
        fruits_arr.add("Apple");
        fruits_arr.add("Grape");
    String[] fruits = fruits_arr.toArray(new String[0]);  
    String s = "My most favorite fruit is [0], but I also like [1] and [3]";
    StringBuffer result = new StringBuffer();
    Matcher m = Pattern.compile("\\[(\\d+)\\]").matcher(s); // Initializing Matcher
    while (m.find()) {                          // Iterate over matches
        int num = Integer.parseInt(m.group(1)); // If there is a match, Group 1 has digits
        String replacement = "";
        if (num < fruits.length) {          // If the number is lower than fruit element count
               replacement =fruits[num];   // Get the array element
        } else {
            replacement = m.group();        // Else, use the whole match (e.g. [9])
        }
        m.appendReplacement(result, replacement); // Append this replacement
    }
    m.appendTail(result);
    System.out.println(result.toString());

With \[(\d+)] you match any substring with [+digits+], and capture the digit sequence into Group 1.

You can use the following:

String str = "My most favorite fruit is [0], but I also like [1] and [3]";
String[] fruits = { "Banana", "Orange", "Apple", "Grape" };

for (int i = 0; i < fruits.length; i++)
{
    str = str.replaceAll("\\[" + i + "\\]", fruits[i]);
}