Separate combined words in a sentence and convert them into Pig Latin
This is in addition to what @thecoder16 already said.

WordSeparator

Methods should be named using verbs instead of nouns.
They usually take some action on the input,
for example this method separates the words that were stuck together.
So separateWords would be better.

Also, this part is not great:


    // Checks for upper case characters
    if(Character.isUpperCase(str.charAt(i)))
    {
        //Inserting space
        str.insert(i, ' '); 
        char ch = Character.toLowerCase(str.charAt(i+1)); 
        str.setCharAt((i+1), ch); 
    }



Objections:


The str.charAt(i) and str.charAt(i+1) refer to the same character. This is repetitive, and can be prone to errors, as you have to remember to use i+1 the second time because of the inserted space
The comments only state the obvious. Unnecessary comments are like noise, and a waste of time to read. Let the code speak for itself.


It would be better this way:

    char ch = str.charAt(i);
    if (Character.isUpperCase(ch)) {
        str.insert(i, ' ');
        str.setCharAt(i + 1, Character.toLowerCase(ch));
    }


PigLatin

The biggest issue here is the latin = latin.concat(...) call for two reasons:


String concatenation is inefficient. You should use a StringBuilder like you did in your other method.
Reusing input parameters is not a good practice, as it can be confusing and error prone. It would be better to name local variables differently.


Issues similar to WordSeparator:


The method is poorly named. Perhaps toPigLatin would be better.
The comments are unnecessary noise


Other smaller issues:


Instead of printing output, it would be better to return the result
The String[] arr is unused, so it would be better to remove it
The counting for loop can be converted to an enhanced loop, for example: for (String str : tokens) { ... }
The input parameter revisedSentence carries information that's unnecessary for the functioning of this method. Just sentence would be enough.