Java ArrayDeque contains(Object) 方法

描述

Java ArrayDeque contains(Object) 方法返回true，如果此deque包含指定的元素。对于自定义对象，应实现equals()方法，以便contains可以正确比较对象。

声明

以下是java.util.ArrayDeque.contains() 方法的声明

public boolean contains(Object o) 

参数

o − 要检查是否包含在deque中的对象。

返回值

如果此deque包含指定的元素，则此方法返回true，否则返回false。

异常

无

检查整数ArrayDeque中元素是否存在示例

以下示例演示了Java ArrayDeque contains()方法的用法。我们使用的是Integer。我们将添加一些元素，然后检查某个元素是否存在。

package com.tutorialspoint;

import java.util.ArrayDeque;
import java.util.Deque;

public class ArrayDequeDemo {
   public static void main(String[] args) {

      // create an empty array deque
      Deque<Integer> deque = new ArrayDeque<>();

      // use add() method to add elements in the deque
      deque.add(20);
      deque.add(30);
      deque.add(10);
      deque.add(18);        

      // let us print all the elements available in deque
      System.out.println("ArrayDeque = " + deque);

      // deque contains element 10
      if (deque.contains(10)) {
         System.out.println("element 10 is present in the deque");
      } else {
         System.out.println("element 10 is not present in the deque");
      }

      // deque does not contain element 25
      if (deque.contains(25)) {
         System.out.println("element 25 is present in the deque");
      } else {
         System.out.println("element 25 is not present in the deque");    
      }
   }
}           

输出

让我们编译并运行上述程序，这将产生以下结果：

ArrayDeque = [20, 30, 10, 18]
element 10 is present in the deque
element 25 is not present in the deque

检查字符串ArrayDeque中元素是否存在示例

以下示例演示了使用字符串的Java ArrayDeque contains()方法的用法。我们将添加一些元素，然后检查某个元素是否存在。

package com.tutorialspoint;

import java.util.ArrayDeque;
import java.util.Deque;

public class ArrayDequeDemo {
   public static void main(String[] args) {

      // create an empty array deque
      Deque<String> deque = new ArrayDeque<>();

      // use add() method to add elements in the deque
      deque.add("Welcome");
      deque.add("to");
      deque.add("tutorialspoint");
      deque.add(".com");        

      // let us print all the elements available in deque
      System.out.println("ArrayDeque = " + deque);

      // deque contains element tutorialspoint
      if (deque.contains("tutorialspoint")) {
         System.out.println("element tutorialspoint is present in the deque");
      } else {
         System.out.println("element tutorialspoint is not present in the deque");
      }

      // deque does not contain element html
      if (deque.contains("html")) {
         System.out.println("element html is present in the deque");
      } else {
         System.out.println("element html is not present in the deque");    
      }
   }
}           

输出

让我们编译并运行上述程序，这将产生以下结果：

ArrayDeque = [Welcome, to, tutorialspoint, .com]
element tutorialspoint is present in the deque
element html is not present in the deque

检查对象ArrayDeque中元素是否存在示例

以下示例演示了使用Student对象的Java ArrayDeque contains()方法的用法。我们将添加一些元素，然后检查某个元素是否存在。

package com.tutorialspoint;

import java.util.ArrayDeque;
import java.util.Deque;

public class ArrayDequeDemo {
   public static void main(String[] args) {

      // create an empty array deque
      Deque<Student> deque = new ArrayDeque<>();

      // use add() method to add elements in the deque
      deque.add(new Student(1, "Julie"));
      deque.add(new Student(2, "Robert"));
      deque.add(new Student(3, "Adam"));      

      // let us print all the elements available in deque
      System.out.println("ArrayDeque = " + deque);

      // deque contains element Robert
      if (deque.contains(new Student(2, "Robert"))) {
         System.out.println("Student Robert is present in the deque");
      } else {
         System.out.println("Student Robert is not present in the deque");
      }

      // deque does not contain element Jane
      if (deque.contains(new Student(4, "Jane"))) {
         System.out.println("Student Jane is present in the deque");
      } else {
         System.out.println("Student Jane is not present in the deque");    
      }
   }
} 
class Student {
   int rollNo;
   String name;

   Student(int rollNo, String name){
      this.rollNo = rollNo;
      this.name = name;
   }

   @Override
   public String toString() {
      return "[ " + this.rollNo + ", " + this.name + " ]";
   }
   
   @Override
   public boolean equals(Object obj) {
      Student s = (Student)obj;
      return this.rollNo == s.rollNo && this.name.equalsIgnoreCase(s.name);
   }
}

输出

让我们编译并运行上述程序，这将产生以下结果：

ArrayDeque = [[ 1, Julie ], [ 2, Robert ], [ 3, Adam ]]
Student Robert is present in the deque
Student Jane is not present in the deque