Strings in Java – String Objects
Strings in Java are objects. They are instances of the class String (in the package java.lang).
As is the case with other objects, String variables are actually references to a String object in
memory. The variable with contain an address, rather than the actual string.
For example, the statement
String friend = new String(“Fred”);
creates a new string as shown in the following diagram.
friend
“Fred”
This constructor is rarely used. Java has an equivalent, simpler form to create and initialize a variable
of type String.
String friend = “Fred”;
The constructor can be useful, however, to create multiple string objects with the same value (but
different instances of each object).
String s1 = “Sample”;
String s2 = new String(s1);
It is also possible for a String variable to be in a state where it does not refer to a string containing
characters. Consider the following:
String s1; // uninitialized
String s2 = null; // null string
String s3 = ""; // empty string
The variable s1 is uninitialized. It can be assigned to a String, but any other attempt to use this
variable will result in an error.
The variable s2 has been set to the null value. It can be printed (producing the output "null") or
compared to other strings.
The variable s3 has been set to the empty string, which has a length of zero and contains no
characters, but is also valid to use with all string operations.
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s1
“Sample”
s2
“Sample”
