CopyOnWriteArrayList的contains(E e)方法检查列表中是否存在给定元素。如果元素至少出现一次,则该函数返回true,否则返回false。
用法:
public boolean contains(Object o)
参数:该函数接受一个强制性参数,该参数指定要在列表中检查其外观的元素。
返回值:如果元素在列表中至少出现一次,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 CopyOnWriteArrayList
// contains() 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.contains(100))
System.out.println("100 is present in the list");
else
System.out.println("100 is not present in the list");
// check using function
if (ArrLis.contains(20))
System.out.println("20 is present in the list");
else
System.out.println("20 is not present in the list");
}
}
输出:
CopyOnWriteArrayList: [32, 67, 98, 100] 100 is present in the list 20 is not present in the list
示例2:
// Java Program to illustrate the CopyOnWriteArrayList
// contains() 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.contains("gfg"))
System.out.println("'gfg' is present in the list");
else
System.out.println("'gfg' is not present in the list");
// check using function
if (ArrLis.contains("best"))
System.out.println("'best' is present in the list");
else
System.out.println("'best' is not present in the list");
}
}
输出:
CopyOnWriteArrayList: [gopal, gfg, jgec, sudo] 'gfg' is present in the list 'best' is not present in the list
参考: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CopyOnWriteArrayList.html#contains-E-
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