Java中的 ArrayDeque forEach() 方法

ArrayDeque的forEach()方法继承自接口Java .lang.Iterable 。如果方法指定了该顺序，则该操作按迭代顺序执行。 Method遍历ArrayDeque的Iterable的每个元素，直到所有元素都被该方法处理完或者发生异常。操作抛出的异常被传递给调用者。

句法：

public void forEach(Consumer action)

参数：此方法采用参数名称action ，它表示要对每个元素执行的操作。

返回：此方法不返回任何内容。

异常：如果指定的操作为空，则此方法抛出NullPointerException 。

下面的程序说明了 ArrayDeque 的 forEach() 方法：

示例 1：演示包含字符串值队列的 ArrayDeque 上的 forEach() 方法。

// Java Program Demonstrate forEach()
// method of ArrayDeque
  
import java.util.*;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // create an ArrayDeque
        // which contains string values
        ArrayDeque cities = new ArrayDeque();
  
        // Add Strings to list
        cities.add("Kolkata");
        cities.add("Delhi");
        cities.add("Bombay");
        cities.add("Pune");
  
        // forEach method of ArrayDeque and
        // print city names
        cities.forEach((n) -> System.out.println(n));
    }
}

输出：

Kolkata
Delhi
Bombay
Pune

示例 2：演示包含对象队列的 ArrayDeque 上的 forEach() 方法。

// Java Program Demonstrate forEach()
// method of ArrayDeque
  
import java.util.*;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // create an ArrayDeque which going to
        // contains a list of Objects
        ArrayDeque list = new ArrayDeque();
  
        // Add Objects to list
        list.add(new batch("CSE", 67));
        list.add(new batch("ECE", 57));
        list.add(new batch("IT", 90));
        list.add(new batch("ME", 78));
  
        // print result
        System.out.println("list of Objects:");
  
        // forEach method of ArrayDeque and
        // print student names
        list.forEach((n) -> print(n));
    }
  
    // printing details of object
    public static void print(batch n)
    {
        System.out.println("*******************************");
        System.out.println("Batch Name is " + n.name);
        System.out.println("No of Students are " + n.noOfStudents);
    }
}
  
// create a class
class batch {
  
    String name;
    int noOfStudents;
  
    batch(String name, int noOfStudents)
    {
        this.name = name;
        this.noOfStudents = noOfStudents;
    }
}

输出：

list of Objects:
*******************************
Batch Name is CSE
No of Students are 67
*******************************
Batch Name is ECE
No of Students are 57
*******************************
Batch Name is IT
No of Students are 90
*******************************
Batch Name is ME
No of Students are 78

示例 3：演示 ArrayDeque 上 forEach() 方法的 NullPointerException。

// Java Program Demonstrate forEach()
// method of ArrayDeque
  
import java.util.*;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // create an ArrayDeque
        // which contains string values
        ArrayDeque cities = new ArrayDeque();
  
        // Add Strings to list
        cities.add("Kolkata");
        cities.add("Delhi");
        cities.add("Bombay");
        cities.add("Pune");
  
        try {
            // forEach method of ArrayDeque and
            // print city names
            cities.forEach(null);
        }
        catch (Exception e) {
            System.out.println("Exception: " + e);
        }
    }
}

输出：

Exception: java.lang.NullPointerException

参考：
Java Java )