第八章 集合泛型

8.1 Collection List Set

• ArrayList

public class List1 {

	public static void main(String[] args) {
		//实例化ArrayList
		List list1 = new ArrayList();
		ArrayList list2 = new ArrayList();
		var list = new ArrayList();
		var list3 = List.of(1,2,3,"hello","php",new Date());
		
		//array list相互转换
		int[] arr = new int[]{1,2,3};
		List lis = new ArrayList(Arrays.asList(arr));
		System.out.println(lis.get(0));
		System.out.println(lis.size());

		
		//增加元素
		list.add("java");
		list.add(100);
		list.add(new Date());
		list.add(0, "javascript");
		
		//输出集合容器中的元素个数
		System.out.println(list.size());
		list.remove(2);//删除一个元素
		list.remove(2);//删除一个元素
		list.add(1,new Date());
		System.out.println(String.format("%1$tF %1$tT",list.get(1)));
		
		//清空集合，删除所有元素  .size() 为0
		//list.clear();
		list.add("python");
		System.out.println(list.indexOf("java"));
		list.set(2, "python");//修改指定索引位置的对象
		
		System.out.println(list.contains("java"));
		System.out.println("-".repeat(50));
		//list.remove("python");
		
		//list.removeIf(e->e.toString().contains("py"));
		//list.removeIf(e->true);
		
		System.out.println(list.size());
		for(Object o : list) {
			System.out.println(o);
		}
		
		Object[] os = list.toArray();
		System.out.println(os.length);
		
		System.out.println("-".repeat(50));
		list.addAll(2, List.of(100,200,300,400,500));//将另一个list增加进来
		list.forEach(System.out::println);
	}
}

• ArrayList和Array数组类型转换

public class List2 {

	public static void main(String[] args) {
		Integer[] nums = new Integer[] { 10, 20, 30, 40, 50 };

		//固定尺寸的List
		List list = Arrays.asList(nums);
		List list2 = List.of(1, 2, 3);
		System.out.println(list.size());
		System.out.println(list2.size());
		//list.clear(); 异常
		//list2.clear(); 异常
		
	    //数组 转 List
		List list3 = new ArrayList(list);
		System.out.println(list3.size());
		list3.add(600);
		list3.addAll(List.of(700,800,900));
		
		System.out.println(list3.size());
		System.out.println(list3);
		System.out.println(Arrays.toString(nums));//数组
		
		//List 转到 数组
		Object[] ns = list3.toArray();
		System.out.println(ns.length);
		for(Object i : ns) {
			System.out.println(i);
		}
	}
}

public class List3 {

	public static void main(String[] args) {

		List list = new ArrayList();
		list.addAll(List.of("java", "php", "python"));
		list.add(0, "html");
		list.add(2, "javascript");
		list.set(3, "mysql");

		System.out.println(list.size());// 5
		System.out.println(list.get(1));// java
		System.out.println(list.indexOf("mysql"));// 3
		System.out.println(list.contains("python"));// true

		// list.forEach(System.out::println);
		list.stream().filter(e -> e.startsWith("java")).forEach(System.out::println);

		for (String s : list) {
			System.out.println(s);
		}

		System.out.println(list);

		Integer[] nn = { 10, 20, 30, 40 };
		System.out.println(nn);
		System.out.println(Arrays.toString(nn));
		System.out.println(List.of(nn));//固定尺寸的List
		System.out.println(new ArrayList(List.of(nn)));//List
		
		
		var lista = new ArrayList(List.of("a","b","c"));
		var listb = new ArrayList(List.of("aa","bb","cc","dd"));
		lista.addAll(listb);
		lista.addAll(listb);
		lista.addAll(listb);
		System.out.println(lista);

	}

}

• HashSet

public class Set1 {

	public static void main(String[] args) throws FileNotFoundException, IOException {
		Set sets = new HashSet();

		sets.add(10);
		sets.add(10);
		sets.add(10);
		sets.add(10);
		sets.add(10);
		// System.out.println(sets.size());

		// sets.clear();
		// sets.contains(10)
		// sets.remove(10);

		// 编写双色球效果
		Random rand = new Random();
		// 生成蓝色 1 （1-16）
		int blue = rand.nextInt(16) + 1;

		// 生成红色 5 （1-33）
		Set reds = new HashSet();
		while (reds.size()  a - b);
		list.add(blue);
		System.out.println(list);

		BufferedImage i = new BufferedImage(350, 100, BufferedImage.TYPE_INT_ARGB);
		Graphics2D g = i.createGraphics();
		g.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_GASP);
		g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
		g.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL, RenderingHints.VALUE_STROKE_DEFAULT);

		g.setFont(new Font("", Font.BOLD, 25));
		g.setStroke(new BasicStroke(3));
		for (int n = 0; n