Summary of traversal methods of list, set, map, queue, deque and stack

List of articles

• One 、List
• Two 、Set
• 3、 ... and 、Map
• Four 、Queue
• 5、 ... and 、Deque
• 6、 ... and 、Stack
• summary

---

One 、 Traverse List

1, Use get(int) Methods through , because List The behavior of is almost identical to that of an array ：List Internal storage elements are stored in order according to the sequence of elements , Each element can determine its position by index ,List The index of is the same as the array , from 0 Start

public class Main {
    public static void main(String[] args) {
        List<String> list =  Arrays.asList(" Hangzhou ", " Beijing ", " Shanghai ", " nanjing ");
        for (int i=0; i<list.size(); i++) {
            String s = list.get(i);
            System.out.println(s);
        }
    }
}

2、 Using Iterators iterator() Traverse ,Iterator Itself an object , But it's made up of List Instance call to iterator() Method .Iterator Object knows how to traverse a List, And different List type , Back to Iterator The objects are also different , But it always has the highest access efficiency .

boolean hasnext() Determine whether the next element      E next() Returns the next element

public class Main {
    public static void main(String[] args) {
        List<String> list = Arrays.asList(" Hangzhou ", " Beijing ", " Shanghai ", " nanjing ");
        for (Iterator<String> it = list.iterator(); it.hasNext(); ) {
            String s = it.next();
            System.out.println(s);
        }
    }
}

Two 、 Traverse Set

  Set yes Collection The following unordered sub interfaces

  characteristic ： disorder 、 No index 、 Can't repeat

1、 Use toArray(), Convert to an array , Traversing an array ;

public class Main {
    public static void main(String[] args) {
        Set<String> set = new HashSet<String>();
        Object[ ] objects = set.toArray();
        for(int i = 0; i < objects.length; i++){
              System.out.println(objects[i]+"");
        }
  }
}

2、 Using Iterators iterator() Traverse

public class Main {
    public static void main(String[] args) {
        Set<String> set = new HashSet<String>();
          for (Iterator<String> it = set.iterator(); it.hasNext(); ) {
               String s = it.next();
            System.out.println(s);
        }
  }
}

3、 Use foeach Loop through

public class Main {
    public static void main(String[] args) {
        Set<String> set = new HashSet<String>();
        for (String s : set){
            System.out.println(s);
        }
   }
}

3、 ... and 、 Traverse Map

1、 Use foreach Loop traversal Map Example of keySet() Method Set aggregate

public class Main {
    public static void main(String[] args) {
        Map<String,Integer> map = new HashMap<>();
        for (String key : map.keySet()){
                Integer value = map.get(key);
                System.out.println(key + "=" + value);
        }
   }
}

2、 Traversal usage foreach Loop traversal Map Object's entrySet() aggregate , It contains every key-value Mapping

public class Main {
    public static void main(String[] args) {
        Map<String,Integer> map= new HashMap<>();
        for(Map.Entry<String,Integer> entry : map.entrySet())){
                      String key = entry.getKey();
                      Integer value = entry.getValue();
                      System.out.println(key + "=" + value);
        }
   }
}

Four 、 Traverse Queue

1、 Use foreach Loop traversal queue

public class Main {
    public static void main(String[] args) {
        Queue<String> queue = new LinkedList<String>();
        for(String temp:queue){
           System.out.println(temp);
        }
   }
}

---

2、 Using Iterators iterator() Traverse

public class Main {
    public static void main(String[] args) {
        Queue<String> queue = new LinkedList<String>();
        Iterator it = queue.iterator();
        while(it.hasnext()){
           System.out.println(it.next);
        }
   }
}

3、 Using the queue Queue Self contained method

boolean isEmpty() Determine whether the element in the queue is empty

E poll() Take out the team leader element and delete

public class Main {
    public static void main(String[] args) {
        Queue<String> queue = new LinkedList<String>();
        while(!queue.isEmpty()){
             System.out.println(queue.poll());
        }
   }
}

5、 ... and 、 Traverse Deque

1、foreach Loop traversal

public class Main {
    public static void main(String[] args) {
        Deque<String> deque = new LinkedList<String>();
        for (String string : deque) {
			System.out.println(string);
		}
   }
}

2、 Use iterators to traverse

public class Main {
    public static void main(String[] args) {
        Deque<String> deque = new LinkedList<String>();
        Iterator<String> it = deque.iterator();
		while(it.hasNext()) {
			System.out.println(it.next());
		}
   }
}

6、 ... and 、 Traverse stack

1、while Loop traversal

​
public class Main {
    public static void main(String[] args) {
        Stack<String> stack = new Stack<String>();
        while(stack.isEmpty()) {
			System.out.println(stack.pop());
		}
   }
}

​

2、foreach Loop traversal

​
public class Main {
    public static void main(String[] args) {
        Stack<String> stack = new Stack<String>();
        Iterator<String> it = stack.iterator();
		while(it.hasNext()) {
			System.out.println(it.next());
		}
   }
}

​

---