java.lang.StringBuilder.ensureCapacity() 方法確保了容量至少等於指定的最小值。如果當前容量小於參數，那麼一個新的內部數組分配容量更大。新的容量較大：

• minimumCapacity參數。
• 舊容量的兩倍，再加上2。

如果 minimumCapacity 參數為非正數，則此方法不執行任何操作，隻是返回。

聲明

以下是java.lang.StringBuilder.ensureCapacity()方法的聲明

public void ensureCapacity(int minimumCapacity)

參數

• minimumCapacity -- 這是最低所需容量。

返回值

This method does not return any value.

異常

• NA

例子

下麵的例子顯示java.lang.StringBuilder.ensureCapacity()方法的使用。

package com.yiibai;

import java.lang.*;

public class StringBuilderDemo {

  public static void main(String[] args) {
  
    StringBuilder str1 = new StringBuilder("tuts point");
    System.out.println("string1 = " + str1);

    // returns the current capacity of the string Builder 1
    System.out.println("Old Capacity = " + str1.capacity());
    /* increases the capacity, as needed, to the specified amount in the 
    given StringBuilder object */
    // returns twice the capacity plus 2
    str1.ensureCapacity(28);
    System.out.println("New Capacity = " + str1.capacity());

    StringBuilder str2 = new StringBuilder("compile online");
    System.out.println("string2 = " + str2);
    // returns the current capacity of string Builder 2
    System.out.println("Old Capacity = " + str2.capacity());
    /* returns the old capacity as the capacity ensured is less than the
    old capacity */
    str2.ensureCapacity(29);
    System.out.println("New Capacity = " + str2.capacity());
  }
}  

讓我們來編譯和運行上麵的程序，這將產生以下結果：

string1 = tuts point
Old Capacity = 26
New Capacity = 54
string2 = compile online
Old Capacity = 30
New Capacity = 30