极客教程Java 数组列表能否包含对同一对象的多个引用
Java中的ArrayList类基本上是一个可调整大小的数组，也就是说，它可以根据我们添加或删除的值动态地增长和缩小。它存在于java.util包中。
我们将讨论在Java中ArrayList是否可以包含对同一对象的多个引用。
java中的ArrayList不提供对同一对象重复引用的检查。因此，我们可以随心所欲地插入同一个对象或对一个对象的引用。如果我们愿意，我们可以借助contains()方法来检查一个元素是否已经存在于ArrayList中。
下面是上述问题陈述的代码实现。
// Java program to demonstrate some functionalities
// of ArrayList
import java.util.ArrayList;
class Employee{
private String name;
private String designation;
// Parameterized constructor for Employee class
public Employee(String name, String designation) {
this.name = name;
this.designation = designation;
}
// Creating getters for Employee class
public String getName() {
return name;
}
public String getDesignation() {
return designation;
}
}
public class GFG {
public static void main(String[] args) {
// Creating Objects of Employee class
Employee e1 = new Employee("Raj","Manager");
Employee e2 = new Employee("Simran", "CEO");
Employee e3 = new Employee("Anish", "CTO");
// Creating an ArrayList of Employee type
ArrayList<Employee> employeeList= new ArrayList<>();
// Inserting the employee objects in the ArrayList
employeeList.add(e1);
employeeList.add(e2);
employeeList.add(e3);
// e1 will be inserted again as ArrayList can store multiple
// reference to the same object
employeeList.add(e1);
// Checking if e2 already exists inside ArrayList
// if it exists then we don't insert it again
if(!employeeList.contains(e2))
employeeList.add(e2);
// ArrayList after insertions: [e1, e2, e3, e1]
// Iterating the ArrayList with the help of Enhanced for loop
for(Employee employee: employeeList){
System.out.println(employee.getName() + " is a " + employee.getDesignation());
}
}
}Java
输出
Raj is a Manager
Simran is a CEO
Anish is a CTO
Raj is a ManagerJava