java--集合--Collection介面
阿新 • • 發佈:2021-06-11
- Collection介面和常用方法
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package com.model.connection; import org.w3c.dom.stylesheets.LinkStyle; import java.util.ArrayList; import java.util.List; /** * @Description:測試類 * @Author: 張紫韓 * @Crete 2021/6/11 8:39 */ public class ConnectionDemo02 { public static void main(String[] args) { List
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Connection介面實現類的遍歷方式
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package com.model.connection; import java.util.ArrayList; import java.util.Iterator; import java.util.List; /** * @Description:測試類 * @Author: 張紫韓 * @Crete 2021/6/11 9:19 */ public class CollectionDemo03 { public static void main(String[] args) { List<Object> list = new ArrayList<>(); list.add(new Books(0,"三國",13.1)); list.add(new Books(1,"水滸",13.2)); list.add(new Books(2,"紅樓",13.3)); System.out.println("list"+list); /** * 第一種遍歷的方式(iterator) * */ Iterator<Object> iterator = list.iterator(); /* while(iterator.hasNext()){ Books books = (Books) iterator.next(); System.out.println(books.toString()); } */ //使用快捷鍵的方式:itit 形成iterator遍歷 // Ctrl + j 顯示所有快捷鍵 while (iterator.hasNext()) { Object next = iterator.next(); System.out.println(next); } // 當我們跳出while迴圈後,如果繼續使用 iterator.next() 獲取下一個元素的會丟擲異常 // iterator.next(); // 如果需要重新遍歷集合需要重置我們的迭代器 iterator=list.iterator(); System.out.println("*******iterator第二次遍歷*********"); while (iterator.hasNext()) { Object next = iterator.next(); System.out.println(next); } /** * 第二種遍歷的方式(增強for迴圈) * * 1.使用增強for迴圈,在Collection集合 * 2.增強for迴圈底層仍然是 迭代器 * 3.增強for迴圈是簡化版本的迭代器遍歷 * 4.可以遍歷陣列和集合 * 5.快捷鍵 I * */ System.out.println("*******第二種遍歷的方式*********"); for (Object book:list){ System.out.println(book); } /* int[] num=new int[]{1,2,3,4,5,6}; for(int i:num){ System.out.println(i); }*/ } } class Books{ private int id; private String name; private double price; @Override public String toString() { return "Books{" + "id=" + id + ", name='" + name + '\'' + ", price=" + price + '}'; } public Books(int id, String name, double price) { this.id = id; this.name = name; this.price = price; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public double getPrice() { return price; } public void setPrice(double price) { this.price = price; } }