Java 中的 ArrayDeque forEach()方法
原文:https://www . geeksforgeeks . org/arraydeque-foreach-method-in-Java/
ArrayDeque 的 forEach() 方法继承自T5【Java . lang . iterable】T6接口。如果方法指定了迭代顺序，则按照迭代顺序执行操作。方法遍历 ArrayDeque 的 Iterable 的每个元素，直到该方法处理完所有元素或者发生异常。操作引发的异常被传递给调用方。
语法:
public void forEach(Consumer<? super E> action)
参数:该方法取一个参数名动作，代表每个元素要执行的动作。
返回:此方法不返回任何内容。
异常:如果指定的动作为空，该方法抛出空指针异常。
下面的程序说明了数组的 forEach()方法:
示例 1: 演示 ArrayDeque 上的 forEach()方法，该方法包含一个字符串值队列。
// 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<String> cities = new ArrayDeque<String>();
// 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));
}
}
Output:
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<batch> list = new ArrayDeque<batch>();
// 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;
}
}
Output:
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<String> cities = new ArrayDeque<String>();
// 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);
}
}
}
Output:
Exception: java.lang.NullPointerException
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