/**
* A really simple class representing a Circle.
*/
public class Circle {
private final double radius;
public Circle(double radius) {
this.radius = radius;
}
public String toString() {
return "Radius: " + this.radius;
}
}
String
class represents character strings. All
string literals in Java programs, such as "abc"
, are
implemented as instances of this class.
String
class represents character strings. All
string literals in Java programs, such as "abc"
, are
implemented as instances of this class.
Strings are constant; their values cannot be changed after they are created. String buffers support mutable strings. Because String objects are immutable they can be shared. For example:
String str = "abc";
is equivalent to:
char data[] = {'a', 'b', 'c'}; String str = new String(data);
Here are some more examples of how strings can be used:
System.out.println("abc"); String cde = "cde"; System.out.println("abc" + cde); String c = "abc".substring(2, 3); String d = cde.substring(1, 2);
The class String
includes methods for examining
individual characters of the sequence, for comparing strings, for
searching strings, for extracting substrings, and for creating a
copy of a string with all characters translated to uppercase or to
lowercase. Case mapping is based on the Unicode Standard version
specified by the Character
class.
The Java language provides special support for the string concatenation operator ( + ), and for conversion of other objects to strings. For additional information on string concatenation and conversion, see The Java Language Specification.
Unless otherwise noted, passing a null
argument to a constructor
or method in this class will cause a NullPointerException
to be
thrown.
A String
represents a string in the UTF-16 format
in which supplementary characters are represented by surrogate
pairs (see the section Unicode
Character Representations in the Character
class for
more information).
Index values refer to char
code units, so a supplementary
character uses two positions in a String
.
The String
class provides methods for dealing with
Unicode code points (i.e., characters), in addition to those for
dealing with Unicode code units (i.e., char
values).
Unless otherwise noted, methods for comparing Strings do not take locale
into account. The Collator
class provides methods for
finer-grain, locale-sensitive String comparison.
javac
compiler
may implement the operator with StringBuffer
, StringBuilder
,
or java.lang.invoke.StringConcatFactory
depending on the JDK version. The
implementation of string conversion is typically through the method toString
,
defined by Object
and inherited by all classes in Java.The toString
method is used to provide a string representation of an object. It is a good idea to write a toString
method for every class you write.
The toString
method is used to provide a string representation of an object. It is a good idea to write a toString
method for every class you write.