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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Frameset//EN""http://www.w3.org/TR/REC-html40/frameset.dtd"><!--NewPage--><HTML><HEAD><!-- Generated by javadoc on Thu Apr 27 23:35:12 PDT 2000 --><TITLE>Java 2 Platform SE v1.3: Class StringBuffer</TITLE><LINK REL ="stylesheet" TYPE="text/css" HREF="../../stylesheet.css" TITLE="Style"></HEAD><BODY BGCOLOR="white"><!-- ========== START OF NAVBAR ========== --><A NAME="navbar_top"><!-- --></A><TABLE BORDER="0" WIDTH="100%" CELLPADDING="1" CELLSPACING="0"><TR><TD COLSPAN=2 BGCOLOR="#EEEEFF" CLASS="NavBarCell1"><A NAME="navbar_top_firstrow"><!-- --></A><TABLE BORDER="0" CELLPADDING="0" CELLSPACING="3"> <TR ALIGN="center" VALIGN="top"> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../overview-summary.html"><FONT CLASS="NavBarFont1"><B>Overview</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="package-summary.html"><FONT CLASS="NavBarFont1"><B>Package</B></FONT></A> </TD> <TD BGCOLOR="#FFFFFF" CLASS="NavBarCell1Rev"> <FONT CLASS="NavBarFont1Rev"><B>Class</B></FONT> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="class-use/StringBuffer.html"><FONT CLASS="NavBarFont1"><B>Use</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="package-tree.html"><FONT CLASS="NavBarFont1"><B>Tree</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../deprecated-list.html"><FONT CLASS="NavBarFont1"><B>Deprecated</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../index-files/index-1.html"><FONT CLASS="NavBarFont1"><B>Index</B></FONT></A> </TD> <TD BGCOLOR="#EEEEFF" CLASS="NavBarCell1"> <A HREF="../../help-doc.html"><FONT CLASS="NavBarFont1"><B>Help</B></FONT></A> </TD> </TR></TABLE></TD><TD ALIGN="right" VALIGN="top" ROWSPAN=3><EM><b>Java<sup><font size=-2>TM</font></sup> 2 Platform<br>Std. Ed. v1.3</b></EM></TD></TR><TR><TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2"> <A HREF="../../java/lang/String.html"><B>PREV CLASS</B></A> <A HREF="../../java/lang/System.html"><B>NEXT CLASS</B></A></FONT></TD><TD BGCOLOR="white" CLASS="NavBarCell2"><FONT SIZE="-2"> <A HREF="../../index.html" TARGET="_top"><B>FRAMES</B></A> <A HREF="StringBuffer.html" TARGET="_top"><B>NO FRAMES</B></A></FONT></TD></TR><TR><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2"> SUMMARY: INNER | FIELD | <A HREF="#constructor_summary">CONSTR</A> | <A HREF="#method_summary">METHOD</A></FONT></TD><TD VALIGN="top" CLASS="NavBarCell3"><FONT SIZE="-2">DETAIL: FIELD | <A HREF="#constructor_detail">CONSTR</A> | <A HREF="#method_detail">METHOD</A></FONT></TD></TR></TABLE><!-- =========== END OF NAVBAR =========== --><HR><!-- ======== START OF CLASS DATA ======== --><H2><FONT SIZE="-1">java.lang</FONT><BR>Class StringBuffer</H2><PRE><A HREF="../../java/lang/Object.html">java.lang.Object</A> | +--<B>java.lang.StringBuffer</B></PRE><DL><DT><B>All Implemented Interfaces:</B> <DD><A HREF="../../java/io/Serializable.html">Serializable</A></DD></DL><HR><DL><DT>public final class <B>StringBuffer</B><DT>extends <A HREF="../../java/lang/Object.html">Object</A><DT>implements <A HREF="../../java/io/Serializable.html">Serializable</A></DL><P>A string buffer implements a mutable sequence of characters. A string buffer is like a <A HREF="../../java/lang/String.html"><CODE>String</CODE></A>, but can be modified. At any point in time it contains some particular sequence of characters, but the length and content of the sequence can be changed through certain method calls. <p> String buffers are safe for use by multiple threads. The methods are synchronized where necessary so that all the operations on any particular instance behave as if they occur in some serial order that is consistent with the order of the method calls made by each of the individual threads involved. <p> String buffers are used by the compiler to implement the binary string concatenation operator <code>+</code>. For example, the code: <p><blockquote><pre> x = "a" + 4 + "c" </pre></blockquote><p> is compiled to the equivalent of: <p><blockquote><pre> x = new StringBuffer().append("a").append(4).append("c") .toString() </pre></blockquote> which creates a new string buffer (initially empty), appends the string representation of each operand to the string buffer in turn, and then converts the contents of the string buffer to a string. Overall, this avoids creating many temporary strings. <p> The principal operations on a <code>StringBuffer</code> are the <code>append</code> and <code>insert</code> methods, which are overloaded so as to accept data of any type. Each effectively converts a given datum to a string and then appends or inserts the characters of that string to the string buffer. The <code>append</code> method always adds these characters at the end of the buffer; the <code>insert</code> method adds the characters at a specified point. <p> For example, if <code>z</code> refers to a string buffer object whose current contents are "<code>start</code>", then the method call <code>z.append("le")</code> would cause the string buffer to contain "<code>startle</code>", whereas <code>z.insert(4, "le")</code> would alter the string buffer to contain "<code>starlet</code>". <p> In general, if sb refers to an instance of a <code>StringBuffer</code>, then <code>sb.append(x)</code> has the same effect as <code>sb.insert(sb.length(), x)</code>. <p> Every string buffer has a capacity. As long as the length of the character sequence contained in the string buffer does not exceed the capacity, it is not necessary to allocate a new internal buffer array. If the internal buffer overflows, it is automatically made larger.<P><DL><DT><B>Since: </B><DD>JDK1.0</DD><DT><B>See Also: </B><DD><A HREF="../../java/io/ByteArrayOutputStream.html"><CODE>ByteArrayOutputStream</CODE></A>, <A HREF="../../java/lang/String.html"><CODE>String</CODE></A>, <A HREF="../../serialized-form.html#java.lang.StringBuffer">Serialized Form</A></DL><HR><P><!-- ======== INNER CLASS SUMMARY ======== --><!-- =========== FIELD SUMMARY =========== --><!-- ======== CONSTRUCTOR SUMMARY ======== --><A NAME="constructor_summary"><!-- --></A><TABLE BORDER="1" CELLPADDING="3" CELLSPACING="0" WIDTH="100%"><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TD COLSPAN=2><FONT SIZE="+2"><B>Constructor Summary</B></FONT></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD><CODE><B><A HREF="../../java/lang/StringBuffer.html#StringBuffer()">StringBuffer</A></B>()</CODE><BR> Constructs a string buffer with no characters in it and an initial capacity of 16 characters.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD><CODE><B><A HREF="../../java/lang/StringBuffer.html#StringBuffer(int)">StringBuffer</A></B>(int length)</CODE><BR> Constructs a string buffer with no characters in it and an initial capacity specified by the <code>length</code> argument.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD><CODE><B><A HREF="../../java/lang/StringBuffer.html#StringBuffer(java.lang.String)">StringBuffer</A></B>(<A HREF="../../java/lang/String.html">String</A> str)</CODE><BR> Constructs a string buffer so that it represents the same sequence of characters as the string argument; in other words, the initial contents of the string buffer is a copy of the argument string.</TD></TR></TABLE> <!-- ========== METHOD SUMMARY =========== --><A NAME="method_summary"><!-- --></A><TABLE BORDER="1" CELLPADDING="3" CELLSPACING="0" WIDTH="100%"><TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor"><TD COLSPAN=2><FONT SIZE="+2"><B>Method Summary</B></FONT></TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> <A HREF="../../java/lang/StringBuffer.html">StringBuffer</A></CODE></FONT></TD><TD><CODE><B><A HREF="../../java/lang/StringBuffer.html#append(boolean)">append</A></B>(boolean b)</CODE><BR> Appends the string representation of the <code>boolean</code> argument to the string buffer.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> <A HREF="../../java/lang/StringBuffer.html">StringBuffer</A></CODE></FONT></TD><TD><CODE><B><A HREF="../../java/lang/StringBuffer.html#append(char)">append</A></B>(char c)</CODE><BR> Appends the string representation of the <code>char</code> argument to this string buffer.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> <A HREF="../../java/lang/StringBuffer.html">StringBuffer</A></CODE></FONT></TD><TD><CODE><B><A HREF="../../java/lang/StringBuffer.html#append(char[])">append</A></B>(char[] str)</CODE><BR> Appends the string representation of the <code>char</code> array argument to this string buffer.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> <A HREF="../../java/lang/StringBuffer.html">StringBuffer</A></CODE></FONT></TD><TD><CODE><B><A HREF="../../java/lang/StringBuffer.html#append(char[], int, int)">append</A></B>(char[] str, int offset, int len)</CODE><BR> Appends the string representation of a subarray of the <code>char</code> array argument to this string buffer.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> <A HREF="../../java/lang/StringBuffer.html">StringBuffer</A></CODE></FONT></TD><TD><CODE><B><A HREF="../../java/lang/StringBuffer.html#append(double)">append</A></B>(double d)</CODE><BR> Appends the string representation of the <code>double</code> argument to this string buffer.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> <A HREF="../../java/lang/StringBuffer.html">StringBuffer</A></CODE></FONT></TD><TD><CODE><B><A HREF="../../java/lang/StringBuffer.html#append(float)">append</A></B>(float f)</CODE><BR> Appends the string representation of the <code>float</code> argument to this string buffer.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> <A HREF="../../java/lang/StringBuffer.html">StringBuffer</A></CODE></FONT></TD><TD><CODE><B><A HREF="../../java/lang/StringBuffer.html#append(int)">append</A></B>(int i)</CODE><BR> Appends the string representation of the <code>int</code> argument to this string buffer.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> <A HREF="../../java/lang/StringBuffer.html">StringBuffer</A></CODE></FONT></TD><TD><CODE><B><A HREF="../../java/lang/StringBuffer.html#append(long)">append</A></B>(long l)</CODE><BR> Appends the string representation of the <code>long</code> argument to this string buffer.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> <A HREF="../../java/lang/StringBuffer.html">StringBuffer</A></CODE></FONT></TD><TD><CODE><B><A HREF="../../java/lang/StringBuffer.html#append(java.lang.Object)">append</A></B>(<A HREF="../../java/lang/Object.html">Object</A> obj)</CODE><BR> Appends the string representation of the <code>Object</code> argument to this string buffer.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> <A HREF="../../java/lang/StringBuffer.html">StringBuffer</A></CODE></FONT></TD><TD><CODE><B><A HREF="../../java/lang/StringBuffer.html#append(java.lang.String)">append</A></B>(<A HREF="../../java/lang/String.html">String</A> str)</CODE><BR> Appends the string to this string buffer.</TD></TR><TR BGCOLOR="white" CLASS="TableRowColor"><TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1"><CODE> int</CODE></FONT></TD><TD><CODE><B><A HREF="../../java/lang/StringBuffer.html#capacity()">capacity</A></B>()</CODE><BR> Returns the current capacity of the String buffer.</TD>⌨️ 快捷键说明
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