java基础[数组及对象数组的扩容]

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//数组的扩容
	public static void main(String[] args) {
		int[] arr = new int[8];
		
		for(int i = 0; i <arr.length; i++) {
			arr[i] = (int) (Math.random() * 20);
		}
		
		//遍历
		for(int temp : arr) {
			System.out.print(temp + " ");
		}
		System.out.println();
//		数组的扩容[常见]
		int[] newArr = new int[(int)(arr.length * 1.5)];//乘1.5 变成double类型，需要强转成int类型
		for(int i = 0; i < arr.length; i++) {
			newArr[i] = arr[i];
		}
		arr = newArr;
		for(int temp : arr) {
			System.out.print(temp + " ");
		}
		System.out.println();
	}

//对象数组的扩容
	public static void main(String[] args) {
		Student[] stuArr = new Student[20];
		
		String[] name1 = {"赵","钱","孙","李","周","吴","郑","王"};
		String[] name2 = {"明","阳","微","男","楠","博","三","歌"};
//		遍历才可以用增强for
		for(int i = 0; i < stuArr.length; i++) {
			int id = i + 1;
			int index1 = (int)(Math.random() * 100) % name1.length;
			int index2 = (int)(Math.random() * 100) % name2.length;
			String name = name1[index1] + name2[index2];
			int grade = (int)(Math.random() * 100) % 6 + 1;
			double score = (int)(Math.random() * 101);
			stuArr[i] = new Student(id,name,grade,score);
		}
//		增强for 数据类型 变量名 ： 数组名
		for(Student temp : stuArr) {
			System.out.println(temp.say());
		}
//		对象数组的扩容
		Student[] newStuArr = new Student[(int)(stuArr.length * 1.5)];
		for(int i = 0; i < stuArr.length; i++) {
			newStuArr[i] = stuArr[i];
		}
		stuArr = newStuArr;
		for(Student temp : stuArr) {
			if(temp != null) {  //解决空指针异常
				System.out.println(temp.say());
			} else {
				System.out.println(temp);
			}			
		}
	}