EnsureCapacity如何在Java中工作？ [英] How does ensureCapacity work in Java?

问题描述

StringBuffer buff1 = new StringBuffer("tuts point");

System.out.println("Old Capacity of buff1 = " + buff1.capacity());
buff1.ensureCapacity(28);
System.out.println("New Capacity of buff1 = " + buff1.capacity());

StringBuffer buff2 = new StringBuffer("compilejksde");

System.out.println("Old Capacity of buff2= " + buff2.capacity());
buff2.ensureCapacity(75);
System.out.println("New Capacity of buff2= " + buff2.capacity());

推荐答案

合约说明以下内容：

确保容量至少等于指定的最小值。
如果当前容量小于参数，则分配一个具有更大容量的新内部
数组。新的容量是
较大的：

Ensures that the capacity is at least equal to the specified minimum. If the current capacity is less than the argument, then a new internal array is allocated with greater capacity. The new capacity is the larger of:

• minimumCapacity参数。


• 两次旧容量加上2.

因此，要解释程序的输出：

So, to explain the output from your program:

Old Capacity of buff1 = 26
New Capacity of buff1 = 54  // Old capacity*2+2 (since it's larger than the argument: 28)
Old Capacity of buff2= 28
New Capacity of buff2= 75   // the argument you gave, 75 (since it's larger than 2*28+2 = 58)

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