CompileTime Vs RunTime Resolution of Strings

Compile-Time Resolution of Strings:

When Strings are created with the help of String literals and ‘+’ operator, they get concatenated at compile time. This is referred to as Compile-Time Resolution of Strings. Compiler eliminates the concatenation operator and optimizes the string.

Example:

Consider the below code:

The above code gets optimized at by the Compiler through Compile-Time Resolution of Strings as:

RunTime Resolution of Strings:

When Strings are created with the help of String literals along with variables and ‘+’ operator, they get concatenated at runtime only, as the value of the variables cannot be predicted beforehand. This is referred to as the RunTime Resolution of Strings.

Example:

Consider the below code:

The above code cannot be optimized at by the Compiler at Compile-Time as the value of variable ‘var’ is unknown. Hence RunTime Resolution of Strings occurs here.

Different scenarios and identifying the type of resolution:

1. Suppose the String is defined using a StringBuffer:

   
   

   
   
   

   String str = (new StringBuffer())                  .append("Beginner")                  .append("for")                  .append("Beginner")                  .toString();

   Type of String Resolution: Run-Time Resolution of String

   Here the compiler cannot resolve at compile time because object creation is a runtime activity. Hence the above string will be resolved at run-time.

2. Suppose the String is defined using a StringBuffer:

   
   

   
   
   

   String str = "Beginner"              + " "              + "for"              + " "              + "Beginner";

   Type of String Resolution: Compile-Time Resolution of String

   Here the compiler can resolve at compile time because given Strings are String Literals. Hence the above string will be resolved at compile-time.

3. Suppose the String is defined in a return statement:

   
   

   
   
   

   public static String func(String var) {     return "Beginner" + var + "Beginner"; }

   Type of String Resolution: Run-Time Resolution of String

   Here the compiler cannot resolve at compile time because the value of the variable ‘var’ is a runtime activity. Hence the above string will be resolved at run-time.