String literals

Strings are very common in programs, so Java optimizes their use. Usually if you need a string in your program you create it as follows. Notice that new is not needed.

String str = "String Literal" ;

This creates a string literal that contains the characters "String Literal". A string literal is an object (of class String). The compiler keeps track of the literals in your program and will reuse the same object if it can. (The compiler will not try to reuse other types of objects. String literals are special.)

For example, say that a program contained the following statements:

String str1, str2;

str1 = "String Literal" ;

str2 = "String Literal" ;

Only one object will be created, containing the characters "String Literal". This is safe, because strings are immutable (so a program will not try to change str1 nor str2 because strings can't be changed). There is no need for two string objects whose content is identical.

This is different from this situation:

String strA, strB;
strA = new String("My String") ;

strB = new String("My String") ;

In the above situation, two objects are created, containing identical data. The compiler does not try to reuse the first object.

String msg1, msg2, msg3;

msg1 = "Look Out!" ;

msg2 = "Look Out!" ;

msg3 = "Look Out!" ;