1. String Class

1. String Class
	Chapter 5. Essencial Classes

1.1. Two classes for strings

String, for constant strings.
StringBuffer, for strings that can change.

Why use String? Because they are constants, Strings are cheaper than StringBuffers and they can be shared.

1.2. Creating Strings and StringBuffers

StringBuffer dest = new StringBuffer(len);
StringBuffer dest = new StringBuffer();

String dest = new String("Destination");

1.3. String literals

"Gobbledy gook."

is equivalent to:

new String("Gobbledy gook.")

1.4. Accessor Methods

charAt()

Figure 5.1. charAt() Method

and

length()

1.5. Modifying StringBuffers

append()

Figure 5.2. Inside the StringBuffer

1.6. Converting Objects to Strings

toString();

All classes inherit toString() from the Object class and many classes override this method to provide an implementation that is meaningful to that class. Implement it in your classes too!

valueOf()

Static member of String that can be used to convert variables of different types to Strings.

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1.7. Strings and the Java Compiler

The Java compiler uses the String and StringBuffer classes behind the scenes to handle literal strings and concatenation.

1.7.1. Literal Strings

"Hello World!"

You can use literal strings anywhere you would use a String object.

System.out.println("I add that you look lovely today.");
int len = "Goodbye Cruel World".length();
String s = "Hola Mundo";

The above construct is equivalent to, but more efficient than, this one, which ends up creating two Strings instead of one:

String s = new String("Hola Mundo");

1.7.2. Concatenation and the + Operator

String cat = "cat";
System.out.println("con" + cat + "enation");

The above example compiles to:

String cat = "cat";
System.out.println(new StringBuffer().append("con").append(cat).append("enation"));

You can also use the + operator to append values to a String that are not themselves Strings:

System.out.println("Java's Number " + 1);

	Caution
	Java Strings are First-class Objects, unlike C or C++ strings which are simply null-terminated arrays of 8-bit characters.

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