StringBuffer
This class represents a mutable string of characters that can grow or shrink as necessary. Its mutability makes it suitable for processing text in place, which is not possible with the immutable String class. Its resizability and the various methods it implements make it easier to use than a char[ ] . Create a StringBuffer with the StringBuffer( ) constructor. You may pass a String that contains the initial text for the buffer to this constructor, but if you do not, the buffer will start out empty. You may also specify the initial capacity for the buffer if you can estimate the number of characters the buffer will eventually hold. The methods of this class are synchronized , which makes StringBuffer objects suitable for use by multiple threads. In Java 5.0 and later, when working with a single thread, StringBuilder is preferred over this class because it does not have the overhead of synchronized methods. StringBuilder implements the same methods as StringBuffer and can be used in the same way. Query the character stored at a given index with charAt( ) and set or delete that character with setCharAt( ) or deleteCharAt( ) . Use length( ) to return the length of the buffer, and use setLength( ) to set the length of the buffer, truncating it or filling it with null characters ('\u0000') as necessary. capacity( ) returns the number of characters a StringBuffer can hold before its internal buffer needs to be reallocated. If you expect a StringBuffer to grow substantially and can approximate its eventual size , you can use ensureCapacity( ) to preallocate sufficient internal storage. Use the various append( ) methods to append text to the end of the buffer. Use insert( ) to insert text at a specified position within the buffer. Note that in addition to strings, primitive values, character arrays, and arbitrary objects may be passed to append( ) and insert( ) . These values are converted to strings before they are appended or inserted. Use delete( ) to delete a range of characters from the buffer and use replace( ) to replace a range of characters with a specified String . Use substring( ) to convert a portion of a StringBuffer to a String . The two versions of this method work just like the same-named methods of String . Call toString( ) to obtain the contents of a StringBuffer as a String object. Or use getChars( ) to extract the specified range of characters from the StringBuffer and store them into the specified character array starting at the specified index of that array. As of Java 1.4, StringBuffer implements CharSequence and so also defines a subSequence( ) method that is like substring( ) but returns its value as a CharSequence . Java 1.4 also added indexOf( ) and lastIndexOf( ) methods that search forward or backward (from the optionally specified index) in a StringBuffer for a sequence of characters that matches the specified String . These methods return the index of the matching string or -1 if no match was found. See also the similarly named methods of String after which these methods are modeled . In Java 5.0, this class has a new constructor and new methods for working with CharSequence objects. It implements the Appendable interface for use with java.util.Formatter and includes new methods for working with 21-bit Unicode characters as int codepoints . String concatenation in Java is performed with the + operator and is implemented, prior to Java 5.0, using the append( ) method of a StringBuffer . In Java 5.0 and later, StringBuilder is used instead. After a string is processed in a StringBuffer object, it can be efficiently converted to a String object for subsequent use. The StringBuffer.toString( ) method is typically implemented so that it does not copy the internal array of characters. Instead, it shares that array with the new String object, making a new copy for itself only if and when further modifications are made to the StringBuffer object. Figure 10-59. java.lang.StringBuffer public final class StringBuffer extends AbstractStringBuilder implements CharSequence, Serializable { // Public Constructors public StringBuffer ( ); public StringBuffer (String str ); public StringBuffer (int capacity ); 5.0 public StringBuffer (CharSequence seq ); // Public Instance Methods public StringBuffer append (String str ); synchronized 1.4 public StringBuffer append (StringBuffer sb ); synchronized 5.0 public StringBuffer append (CharSequence s ); public StringBuffer append (Object obj ); synchronized public StringBuffer append (char[ ] str ); synchronized public StringBuffer append (long lng ); synchronized public StringBuffer append (float f ); synchronized public StringBuffer append (double d ); synchronized public StringBuffer append (boolean b ); synchronized public StringBuffer append (char c ); synchronized public StringBuffer append (int i ); synchronized public StringBuffer append (char[ ] str , int offset , int len ); synchronized 5.0 public StringBuffer append (CharSequence s , int start , int end ); synchronized 5.0 public StringBuffer appendCodePoint (int codePoint ); synchronized public char charAt (int index ); Implements: CharSequence synchronized 1.2 public StringBuffer delete (int start , int end ); synchronized 1.2 public StringBuffer deleteCharAt (int index ); synchronized public StringBuffer insert (int offset , char c ); synchronized public StringBuffer insert (int offset , boolean b ); public StringBuffer insert (int offset , long l ); public StringBuffer insert (int offset , int i ); public StringBuffer insert (int offset , String str ); synchronized public StringBuffer insert (int offset , Object obj ); synchronized 5.0 public StringBuffer insert (int dstOffset , CharSequence s ); public StringBuffer insert (int offset , char[ ] str ); synchronized public StringBuffer insert (int offset , double d ); public StringBuffer insert (int offset , float f ); 1.2 public StringBuffer insert (int index , char[ ] str , int offset , int len ); synchronized 5.0 public StringBuffer insert (int dstOffset , CharSequence s , int start , int end ); synchronized public int length ( ); Implements: CharSequence synchronized 1.2 public StringBuffer replace (int start , int end , String str ); synchronized public StringBuffer reverse ( ); synchronized public String toString ( ); Implements: CharSequence synchronized // Methods Implementing CharSequence public char charAt (int index ); synchronized public int length ( ); synchronized 1.4 public CharSequence subSequence (int start , int end ); synchronized public String toString ( ); synchronized // Public Methods Overriding AbstractStringBuilder public int capacity ( ); synchronized 5.0 public int codePointAt (int index ); synchronized 5.0 public int codePointBefore (int index ); synchronized 5.0 public int codePointCount (int beginIndex , int endIndex ); synchronized public void ensureCapacity (int minimumCapacity ); synchronized public void getChars (int srcBegin , int srcEnd , char[ ] dst , int dstBegin ); synchronized 1.4 public int indexOf (String str ); 1.4 public int indexOf (String str , int fromIndex ); synchronized 1.4 public int lastIndexOf (String str ); 1.4 public int lastIndexOf (String str , int fromIndex ); synchronized 5.0 public int offsetByCodePoints (int index , int codePointOffset ); synchronized public void setCharAt (int index , char ch ); synchronized public void setLength (int newLength ); synchronized 1.2 public String substring (int start ); synchronized 1.2 public String substring (int start , int end ); synchronized 5.0 public void trimToSize ( ); synchronized } Passed ToToo many methods to list. Returned ByToo many methods to list.  |
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