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<div class="subTitle">java.lang</div>
<h2 title="Class String" class="title">Class String</h2>
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<li><a href="../../java/lang/Object.html" title="class in java.lang">java.lang.Object</a></li>
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<li>java.lang.String</li>
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<dt>All Implemented Interfaces:</dt>
<dd><a href="../../java/io/Serializable.html" title="interface in java.io">Serializable</a>, <a href="../../java/lang/CharSequence.html" title="interface in java.lang">CharSequence</a>, <a href="../../java/lang/Comparable.html" title="interface in java.lang">Comparable</a>&lt;<a href="../../java/lang/String.html" title="class in java.lang">String</a>&gt;</dd>
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<pre>public final class <span class="strong">String</span>
extends <a href="../../java/lang/Object.html" title="class in java.lang">Object</a>
implements <a href="../../java/io/Serializable.html" title="interface in java.io">Serializable</a>, <a href="../../java/lang/Comparable.html" title="interface in java.lang">Comparable</a>&lt;<a href="../../java/lang/String.html" title="class in java.lang">String</a>&gt;, <a href="../../java/lang/CharSequence.html" title="interface in java.lang">CharSequence</a></pre>
<div class="block">The <code>String</code> class represents character strings. All
string literals in Java programs, such as <code>"abc"</code>, are
implemented as instances of this class.
<p>
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:
<p><blockquote><pre>
String str = "abc";
</pre></blockquote><p>
is equivalent to:
<p><blockquote><pre>
char data[] = {'a', 'b', 'c'};
String str = new String(data);
</pre></blockquote><p>
Here are some more examples of how strings can be used:
<p><blockquote><pre>
System.out.println("abc");
String cde = "cde";
System.out.println("abc" + cde);
String c = "abc".substring(2,3);
String d = cde.substring(1, 2);
</pre></blockquote>
<p>
The class <code>String</code> 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 <a href="../../java/lang/Character.html" title="class in java.lang"><code>Character</code></a> class.
<p>
The Java language provides special support for the string
concatenation operator (&nbsp;+&nbsp;), and for conversion of
other objects to strings. String concatenation is implemented
through the <code>StringBuilder</code>(or <code>StringBuffer</code>)
class and its <code>append</code> method.
String conversions are implemented through the method
<code>toString</code>, defined by <code>Object</code> and
inherited by all classes in Java. For additional information on
string concatenation and conversion, see Gosling, Joy, and Steele,
<i>The Java Language Specification</i>.
<p> Unless otherwise noted, passing a <tt>null</tt> argument to a constructor
or method in this class will cause a <a href="../../java/lang/NullPointerException.html" title="class in java.lang"><code>NullPointerException</code></a> to be
thrown.
<p>A <code>String</code> represents a string in the UTF-16 format
in which <em>supplementary characters</em> are represented by <em>surrogate
pairs</em> (see the section <a href="Character.html#unicode">Unicode
Character Representations</a> in the <code>Character</code> class for
more information).
Index values refer to <code>char</code> code units, so a supplementary
character uses two positions in a <code>String</code>.
<p>The <code>String</code> class provides methods for dealing with
Unicode code points (i.e., characters), in addition to those for
dealing with Unicode code units (i.e., <code>char</code> values).</div>
<dl><dt><span class="strong">Since:</span></dt>
<dd>JDK1.0</dd>
<dt><span class="strong">See Also:</span></dt><dd><a href="../../java/lang/Object.html#toString()"><code>Object.toString()</code></a>,
<a href="../../java/lang/StringBuffer.html" title="class in java.lang"><code>StringBuffer</code></a>,
<a href="../../java/lang/StringBuilder.html" title="class in java.lang"><code>StringBuilder</code></a>,
<a href="../../java/nio/charset/Charset.html" title="class in java.nio.charset"><code>Charset</code></a>,
<a href="../../serialized-form.html#java.lang.String">Serialized Form</a></dd></dl>
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