这个 isEmpty(E) 方法 CopyOnWriteArrayList 检查列表是否为空。如果列表为空,则返回true,否则返回false。
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语法:
public boolean isEmpty()
参数: 该函数不接受任何参数。
返回值: 函数返回 符合事实的 如果列表为空,则返回false。
以下程序说明了上述功能:
项目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
项目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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