List study notes-a little common sense of Java every day

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List collection overview

• Ordered collection (sequence), users can precisely control the insertion position of each element in the list.
• Users can index anti-question elements by integer index and search for elements in the list
• Unlike the Set collection, the stored elements can be repeated
• Orderly and repeatable

List collection-specific methods (inherit all methods of the parent class Collection)

Method name	Description
void add(int index,E element)	Insert the specified element at the specified position in this collection
E remove(int index)	Delete the element at the specified index and return the deleted element
E set(int index,E element)	Modify the element at the specified index and return the modified element
E get(int index)	Returns the element at the specified index

Three kinds of traversal of List collection

• Method 1: Iterator: a unique traversal method for collections
• Method 2: ordinary for; traversal with index
• Method 3: Enhanced for (foreach) (another form of Iterator); the most convenient way of traversal The relationship between the two can be seen
  through concurrent modification of exceptions

import java.util.*;

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

		//创建集合对象
		List<String> list = new ArrayList<String>();
		//添加元素
		list.add("hello");
		list.add("world");

		//方法一：迭代器:集合特有的遍历方式
		Iterator<String> it = list.iterator();
		while (it.hasNext()) {
    
    
			String s = it.next();
			System.out.println(s);
		}
		System.out.println("---------------");
		//方法二：普通for;带有索引的遍历方式
		for(int i=0; i<list.size();i++) {
    
    
			String s = list.get(i);
			System.out.println(s);
		}
		System.out.println("---------------");
		//方法三：增强for;最方便的遍历方式
		for(String s : list) {
    
    
			System.out.println(s);
		}
		
	}
}