convert a string to a list of object using Java 8

Use map(...) method to perform transformations on the original String. Instead of calling Fruit::valueOf through a method reference, split each string on space inside map(...), and construct a combined string when you get exactly two parts:

List<Fruit> f = pattern.splitAsStream("Red apple, blue banana, orange")
.map(s -> {
    String[] parts = s.split(" ");
    String tmp = parts.length == 2
    ? parts[0]+"_"+parts[1]
    : s;
    return Fruit.valueOf(tmp.toUpperCase());
}).collect(Collectors.toList());

Demo.

If you need to perform any additional transformations of the result, you can do them in the same lambda code block prior to the return statement.

Your Enum

static enum Fruit {
    RED_APPLE, BLUE_BANANA, ORANGE
}

Main code:

public static void main(String[] ar) throws Exception {
    Pattern pattern = Pattern.compile(", ");
    List<Fruit> f = pattern.splitAsStream("Red apple, blue banana, orange")
            .map(YourClass::mapToFruit)
            .collect(Collectors.toList());
    System.out.println(f);
}

Helper method to offload dirty mapping part

private static Fruit mapToFruit(String input) {
    String[] words = input.split("\\s");
    StringBuilder sb = new StringBuilder();
    if (words.length > 1) {
        for (int i = 0; i < words.length - 1; i++) {
            sb.append(words[i].toUpperCase());
            sb.append("_");
        }
        sb.append(words[words.length - 1].toUpperCase());
    } else {
        sb.append(words[0].toUpperCase());
    }
    return Fruit.valueOf(sb.toString());
}

Here is another sample:

f = pattern.splitAsStream(fruitString) 
        .map(s -> Arrays.stream(s.split(" ")).map(String::toUpperCase).collect(Collectors.joining("_"))) 
        .map(Fruit::valueOf).collect(Collectors.toList());

Or by StreamEx:

StreamEx.split(fruitString, ", ")
        .map(s -> StreamEx.split(s, " ").map(String::toUpperCase).joining("_"))
        .map(Fruit::valueOf).toList();

String yourString = "Red apple, blue banana, orange";
stringArray = yourString.split(", ");
List<string> result;
//stringArray will contain 3 strings
//Red apple
//blue banana
//orange
for(string s : stringArray) {
    //Replace all spaces with underscores
    result.add(s.replace(" ", "_").toUpperCase());
}

To split the string you can do:

string[] output = fruitString.split(",");

You would then have to go through the string letter by letter to find spaces and replace them with strings:`

for(int i = 0; i < output.length; i++){
   for(int j = 0; j < output[i].length(); j++){
       char c = output[i].charAt(j);
       //check for space and replace with _
   }
}

then using the .toUpperCase() to conver the first char to a upper letter

Hope this helps you.

Please find the below Code, I have followed the below Steps :

1) Split the String by , first.

2) Again split the result of 1) String by " ".

3) Then if the word counts are more than 1 then only proceed to append the underscore.

Demo: http://rextester.com/NNDF87070

import java.util.*;
import java.lang.*;

class Rextester
{  
       public static int WordCount(String s){

        int wordCount = 0;

        boolean word = false;
        int endOfLine = s.length() - 1;

        for (int i = 0; i < s.length(); i++) {
            // if the char is a letter, word = true.
            if (Character.isLetter(s.charAt(i)) && i != endOfLine) {
                word = true;
                // if char isn't a letter and there have been letters before,
                // counter goes up.
            } else if (!Character.isLetter(s.charAt(i)) && word) {
                wordCount++;
                word = false;
                // last word of String; if it doesn't end with a non letter, it
                // wouldn't count without this.
            } else if (Character.isLetter(s.charAt(i)) && i == endOfLine) {
                wordCount++;
            }
        }
        return wordCount;
    }
    public static void main(String args[])
    {
         String cord = "Red apple , blue banana, orange";
        String[] parts = cord.split(",");
        String[] result1 = new String[parts.length];
        for(int i=0; i<parts.length;i++) {

            String[] part2 = parts[i].split(" ");

            if(parts[i].length() > 1 && WordCount(parts[i]) > 1)
            {
                String result = "_";
                String uscore = "_";
                for(int z =0; z < part2.length; z++)
                {
                    if(part2.length > 1 ) {
                        if (z + 1 < part2.length) {
                            result = part2[z] + uscore + part2[z + 1];
                        }
                    }
                }

                result1[i] = result.toUpperCase();
            }
            else
            {
                result1[i] = parts[i];
            }

        }

         for(int j =0 ; j <parts.length; j++)
        {
            System.out.println(result1[j]);
        }

    }
}

References for the WordCount Method: Count words in a string method?