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J2ME in a Nutshell by Kim Topley

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Name

StringBuffer

Synopsis

A StringBuffer is an array of characters that can be expanded or contracted as necessary. StringBuffers are typically used to construct an array of characters that is then converted into an immutable String.

The characters that make up the content of a StringBuffer are held in an internal array. The number of entries in the array is referred to as the capacity of the StringBuffer, while the actual number of characters in use is referred to as its size. A StringBuffer is constructed with a specific initial capacity (the default is 16 characters). It can also be constructed from the content of a String, in which case an appropriate initial capacity is determined. When the size approaches the capacity, a new character array is allocated and the existing characters are copied into it. Note that this can be a costly operation that may have to be repeated if the StringBuffer’s size grows continuously. If possible, the StringBuffer should be created with sufficient capacity to hold all of the characters that it will contain.

Following construction, the ensureCapacity() method is used to ensure that the internal array can hold at least the number of characters specified without needing to be expanded any further. capacity() returns the current capacity of the StringBuffer, while length() returns its actual size. The actual number of characters in use can be changed by calling the setLength() method. If the new length is smaller than the old length, the characters ...

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