If your code passes the wrong element to the method, the code compiles fine, but might raise a runtime error or silently return no results.
如果代码给方法传递错误的元素，那么尽管代码将编绎良好，但可能会导致运行时错误或者不返回任何结果。
It should return false if no changes are made. The example code in Listing 8 shows this logic.
如果没有进行修改，就应该返回false。
The four lines of code at the bottom of Listing 1 prove that no matter how many times you ask for an instance of the ConnPool pool class, it will always return the same object.
清单1底部的四行代码则证明无论请求ConnPool池类的一个实例多少次，它都会返回相同的对象。
The four lines of code at the bottom of Listing 1 prove that no matter how many times you ask for an instance of the ConnPool pool class, it will always return the same object.
清单1底部的四行代码则证明无论请求ConnPool池类的一个实例多少次，它都会返回相同的对象。
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