Java 翻译 StringBuffer
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A thread-safe, mutable sequence of characters. A string buffer is like a
String, but can be modified. At any point in time(任何时候) it contains some particular(特定的) sequence of characters, but the length and content of the sequence can be changed through certain(某些) method calls(调用). String buffers are safe for use by multiple threads. The methods are synchronized where necessary(必要的) so that all the operations on any particular instance behave as if they occur(发生) in some serial order that is consistent(一致的) with the order of the method calls made by each of the individual threads involved(涉及).
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The principal(主要) operations(操作) on a StringBuffer are the append and insert methods, which are overloaded so as to accept(接受) data of any type. Each effectively(有效) converts a given(特定) datum(基准) to a string and then appends or inserts the characters of that string to the string buffer. The append method always adds these characters at the end of the buffer; the insert method adds the characters at a specified point.
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For example(例如), if z refers(指) to a string buffer object whose(其) current contents are "start", then the method call z.append("le") would cause(导致) the string buffer to contain "startle", whereas(而) z.insert(4, "le") would alter the string buffer to contain "starlet".
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In general(一般), if sb refers to an instance(实例) of a StringBuffer, then sb.append(x) has the same effect(效果) as sb.insert(sb.length(),?x).
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Whenever(每当) an operation(操作) occurs involving a source sequence (such(比如) as appending or inserting from a source sequence) this class synchronizes only on the string buffer performing(执行) the operation, not on the source.
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Every string buffer has a capacity(容量). As long as the length of the character sequence contained in the string buffer does not exceed(超过) the capacity(容量), it is not necessary(必要) to allocate(分配) a new internal(内部) buffer array. If the internal(内部) buffer overflows, it is automatically made larger. As of release JDK 5, this class has been supplemented(补充) with an equivalent(等价) class designed(设计) for use by a single thread, StringBuilder. The StringBuilder class should generally(一般) be used in preference(优先) to this one, as it supports all of the same operations but it is faster, as it performs no synchronization.