Java ArrayList ensureCapacity()方法及实例
java.util.ArrayList 类的 ensureCapacity() 方法在必要时增加该ArrayList实例的容量,以确保它至少可以容纳由最小容量参数指定的元素数量。
语法
public void ensureCapacity(int minCapacity)
Java
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 ArrayList<Integer>
ArrayList<Integer>
arrlist = new ArrayList<Integer>();
// adding element to arrlist
arrlist.add(10);
arrlist.add(20);
arrlist.add(30);
arrlist.add(40);
// Print the ArrayList
System.out.println("ArrayList: "
+ arrlist);
// ensure that the ArrayList
// can hold upto 5000 elements
// using ensureCapacity() method
arrlist.ensureCapacity(5000);
// Print
System.out.println("ArrayList can now"
+ " surely store upto"
+ " 5000 elements.");
}
catch (NullPointerException e) {
System.out.println("Exception thrown : " + e);
}
}
}
Java
输出。
ArrayList: [10, 20, 30, 40]
ArrayList can now surely store upto 5000 elements.
Java
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 ArrayList<Integer>
ArrayList<String>
arrlist = new ArrayList<String>();
// adding element to arrlist
arrlist.add("A");
arrlist.add("B");
arrlist.add("C");
arrlist.add("D");
// Print the ArrayList
System.out.println("ArrayList: "
+ arrlist);
// ensure that the ArrayList
// can hold upto 400 elements
// using ensureCapacity() method
arrlist.ensureCapacity(400);
// Print
System.out.println("ArrayList can now"
+ " surely store upto"
+ " 400 elements.");
}
catch (NullPointerException e) {
System.out.println("Exception thrown : " + e);
}
}
}
Java
输出。
ArrayList: [A, B, C, D]
ArrayList can now surely store upto 400 elements.
Java