Java StringBuffer ensureCapacity()方法及示例
StringBuffer类 的 ensureCapacity() 方法确保其容量至少等于指定的minimumCapacity。
如果StringBuffer的当前容量小于参数minimumCapacity，那么将分配一个新的内部数组，容量更大。如果minimumCapacity参数>旧容量的两倍，再加上2，那么新容量等于minimumCapacity，否则新容量等于旧容量的两倍，再加上2。如果作为参数传递的minimumCapacity参数<0，该方法不采取任何行动。语法
public void ensureCapacity(int minimumCapacity)
参数： 该方法需要一个参数 minimumCapacity ，它是所需的最小容量。
返回值： 该方法不返回任何东西。下面的程序演示了StringBuffer类的ensureCapacity()方法
例1 :
// Java program to demonstrate// the ensureCapacity() Method. class GFG { public static void main(String[] args) { // create a StringBuffer object StringBuffer str = new StringBuffer(); // print string capacity System.out.println("Before ensureCapacity " + "method capacity = " + str.capacity()); // apply ensureCapacity() str.ensureCapacity(18); // print string capacity System.out.println("After ensureCapacity" + " method capacity = " + str.capacity()); }}
输出
Before ensureCapacity method capacity = 16After ensureCapacity method capacity = 34
例2 :
// Java program to demonstrate// the ensureCapacity() Method. class GFG { public static void main(String[] args) { // create a StringBuffer object StringBuffer str = new StringBuffer("Geeks For Geeks"); // print string capacity System.out.println("Before ensureCapacity " + "method capacity = " + str.capacity()); // apply ensureCapacity() str.ensureCapacity(42); // print string capacity System.out.println("After ensureCapacity" + " method capacity = " + str.capacity()); }}
输出
Before ensureCapacity method capacity = 31After ensureCapacity method capacity = 64
参考文献： https://docs.oracle.com/javase/10/docs/api/java/lang/StringBuffer.html#ensureCapacity(int)
