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I wonder why the double quotation marks is not shown in the actual output - just after the equal sign:
String word = "" + c1 + c2 + "ll";

The full code as follows:
public class InstantMethodsIndexOf
    public void start()
        String greeting = new String ("Hello World");

        int position = greeting.indexOf('r');
        char c1 = greeting.charAt(position + 2);
        char c2 = greeting.charAt(position - 1);

        String word = "" + c1 + c2 + "ll";

Updated 4-Jul-14 17:21pm
Sergey Alexandrovich Kryukov 5-Jul-14 0:41am    
By the same reason +, =, and blank space are not shown — they are not part of string, they are part of syntax.
By the way, always use string.Empty instead of "".
DamithSL 5-Jul-14 1:14am    
You are correct, initially I thought OP need to know why there is "" used. I have change my answer.

"" is empty string and it will not adding anything to your final word object.
if it is not adding anything why there is ""?
The ‘+’ operator in java is overloaded as a String concatenator. Anything added to a String object using the ‘+’ operator becomes a String. Since c1 and c2 are char types, once you summed up them with '+' the result will be the addition of char codes of values in the two variable (ex. 'a' + 'b' produces 195). You can convert these chars to strings by start concatenation with empty string.

""+'a' is equal to "a".
and then "a"+'b' is equal to "ab".

This is applicable to any numeric data type.

for example: below will give error: incompatible types
String x = 5+7; //error: incompatible types

String x = ""+ 5+7;// successfully compile and give you 57

read:Is concatenating with an empty string to do a string conversion really that bad?[^]
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why u use ""? only u can use '+' operator for concatenation
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