Java Vector ensureCapacity()方法及示例

Java.util.Vector 类的 ensureCapacity() 方法在必要时增加该Vector实例的容量，以确保它至少能容纳最小容量参数所指定的元素数量。

语法

public void ensureCapacity(int minCapacity)

参数： 该方法将 所需的最小容量 作为参数。

下面是一些例子来说明 ensureCapacity() 方法。

例1 :

// Java program to demonstrate
// ensureCapacity() method for Integer value
  
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv)
        throws Exception
    {
  
        try {
  
            // Creating object of Vector<Integer>
            Vector<Integer>
                vector = new Vector<Integer>();
  
            // adding element to vector
            vector.add(10);
            vector.add(20);
            vector.add(30);
            vector.add(40);
  
            // Print the Vector
            System.out.println("Vector: "
                               + vector);
  
            // ensure that the Vector
            // can hold upto 5000 elements
            // using ensureCapacity() method
            vector.ensureCapacity(5000);
  
            // Print
            System.out.println("Vector can now"
                               + " surely store upto"
                               + " 5000 elements.");
        }
  
        catch (Exception e) {
            System.out.println(e);
        }
    }
}

输出：

Vector: [10, 20, 30, 40]
Vector can now surely store upto 5000 elements.

例2 :

// Java program to demonstrate
// ensureCapacity() method for String value
  
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv)
        throws Exception
    {
  
        try {
  
            // Creating object of Vector<Integer>
            Vector<String>
                vector = new Vector<String>();
  
            // adding element to vector
            vector.add("A");
            vector.add("B");
            vector.add("C");
            vector.add("D");
  
            // Print the Vector
            System.out.println("Vector: "
                               + vector);
  
            // ensure that the Vector
            // can hold upto 400 elements
            // using ensureCapacity() method
            vector.ensureCapacity(400);
  
            // Print
            System.out.println("Vector can now"
                               + " surely store upto"
                               + " 400 elements.");
        }
  
        catch (Exception e) {
            System.out.println(e);
        }
    }
}

输出：

Vector: [A, B, C, D]
Vector can now surely store upto 400 elements.