Java StringBuilder ensureCapacity()用法及代碼示例

StringBuilder類的suresureCapacity(int minimumCapacity)方法可幫助我們確保容量至少等於作為參數傳遞給方法的指定minimumCapacity。

如果StringBuilder的當前容量小於參數minimumCapacity，則將分配一個具有更大容量的新內部數組。
如果minimumCapacity參數大於舊容量的兩倍加2，則新容量等於MinimumCapacity，否則新容量等於舊容量的兩倍加2。
如果作為參數傳遞的minimumCapacity參數為not-positive，則此方法不執行任何操作。

用法:

public void ensureCapacity(int minimumCapacity)

參數：此方法接受一個參數minimumCapacity，它表示所需的最小所需容量。

返回值：此方法不返回任何內容。

下麵的程序演示StringBuilder類的ensureCapacity()方法：

示例1:

在此程序中，等於18的minimumCapacity自變量小於舊容量的兩倍，加上等於34的2則新容量等於34。

// Java program to demonstrate 
// the ensureCapacity() Method. 
  
class GFG { 
    public static void main(String[] args) 
    { 
        // create a StringBuilder object 
        StringBuilder str = new StringBuilder(); 
  
        // 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()); 
    } 
}

輸出：

Before ensureCapacity method capacity = 16
After ensureCapacity method capacity = 34

示例2:

在此程序中，等於44的minimumCapacity參數大於舊容量的兩倍，再加上等於34的2，則新容量等於34。

// Java program to demonstrate 
// the ensureCapacity() Method. 
  
class GFG { 
    public static void main(String[] args) 
    { 
  
        // create a StringBuilder object 
        StringBuilder str = new StringBuilder(); 
  
        // print string capacity 
        System.out.println("Before ensureCapacity"
                           + " method capacity = "
                           + str.capacity()); 
  
        // apply ensureCapacity() 
        str.ensureCapacity(44); 
  
        // print string capacity 
        System.out.println("After ensureCapacity"
                           + " method capacity = "
                           + str.capacity()); 
    } 
}

輸出：

Before ensureCapacity method capacity = 16
After ensureCapacity method capacity = 44

參考：
https://docs.oracle.com/javase/10/docs/api/java/lang/StringBuilder.html#ensureCapacity(int)

相關用法

注：本文由純淨天空篩選整理自AmanSingh2210大神的英文原創作品 StringBuilder ensureCapacity() in Java with Examples。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。