CopyOnWriteArrayList的isEmpty(E e)方法检查列表是否为空。如果列表为空,则返回true,否则返回false。
用法:
public boolean isEmpty()
参数:该函数不接受任何参数。
返回值:如果列表为空,则该函数返回true,否则返回false。
以下示例程序旨在说明上述函数:
示例1:
// Java Program to illustrate the
// isEmpty() method in Java
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// create object of CopyOnWriteArrayList
CopyOnWriteArrayList<Integer> ArrLis
= new CopyOnWriteArrayList<Integer>();
// Add elements
ArrLis.add(32);
ArrLis.add(67);
ArrLis.add(98);
ArrLis.add(100);
// print CopyOnWriteArrayList
System.out.println("CopyOnWriteArrayList: " + ArrLis);
// check using function
if (ArrLis.isEmpty())
System.out.println("List is empty");
else
System.out.println("List is not empty");
ArrLis.clear();
// check using function
if (ArrLis.isEmpty())
System.out.println("List is empty");
else
System.out.println("List is not empty");
}
}
输出:
CopyOnWriteArrayList: [32, 67, 98, 100] List is not empty List is empty
示例2:
// Java Program to illustrate the
// isEmpty() method in Java
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// create object of CopyOnWriteArrayList
CopyOnWriteArrayList<String> ArrLis
= new CopyOnWriteArrayList<String>();
// Add elements
ArrLis.add("gopal");
ArrLis.add("gfg");
ArrLis.add("jgec");
ArrLis.add("sudo");
// print CopyOnWriteArrayList
System.out.println("CopyOnWriteArrayList: " + ArrLis);
// check using function
if (ArrLis.isEmpty())
System.out.println("List is empty");
else
System.out.println("List is not empty");
ArrLis.clear();
// check using function
if (ArrLis.isEmpty())
System.out.println("List is empty");
else
System.out.println("List is not empty");
}
}
输出:
CopyOnWriteArrayList: [gopal, gfg, jgec, sudo] List is not empty List is empty
参考: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CopyOnWriteArrayList.html#isEmpty–
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