java 引用类型的数据传递的是内存地址实例

public class Test2 {
	// java中引用类型的数据传递的是内存地址
	private Map<String, Student> students = new Hashtable<String, Student>(); 
	public void myTest() {
		Student student1 = new Student("令狐冲", 16, "华山派", 19888.66);
		Student student2 = new Student("韦小宝", 15, "紫禁城", 99999.99);
		Student student3 = new Student("张无忌", 18, "光明顶", 18888.88);
		students.put("1", student1);
		students.put("2", student2);
		students.put("3", student3);
		Iterator<Map.Entry<String, Student>> entries = students.entrySet().iterator();
		while (entries.hasNext()) {
			Map.Entry<String, Student> entry = entries.next();
			System.out.println("Key = " + entry.geTKEy() + ", Value = " + entry.getValue());
			entry.getValue().setAge(entry.getValue().getAge() + 1);
		} 
	}
	
	public void myTest2(){
		List<String[]> citys = new ArrayList<String[]>();
		String [] cityNames = {"赣州市", "于都县", "江西省", "中国", "赣南地区"};
		citys.add(cityNames);
		for (int index = 0; index < citys.size(); index++) {
			String[] mycityNames = citys.get(index);
			for (int i = 0; i < mycityNames.length; i++) {
				System.out.println(mycityNames[i]);	
				if (i == 1) {
					//修改mycityNames数组 (java中引用类型的数据传递的是内存地址)
					mycityNames[i] = "我们" + mycityNames[i];
				}
			}
			
			System.out.println("--------------------------------");			
			for (int i = 0; i < mycityNames.length; i++) {
				System.out.println(mycityNames[i]);	
			}			
		}
		System.out.println("--------------------------------");
		//修改cityNames数组 (java中引用类型的数据传递的是内存地址)
		cityNames[0] = "我们赣州市";
		
		for (int index = 0; index < citys.size(); index++) {
			String[] mycityNames = citys.get(index);
			for (int i = 0; i < mycityNames.length; i++) {
				System.out.println(mycityNames[i]);	
			}
		}
	}
 
	public static void main(String[] args) {
		Test2 test2 = new Test2();
		test2.myTest();
		System.out.println("--------------------------------");
		Iterator<Map.Entry<String, Student>> entries = test2.students.entrySet().iterator();
		while (entries.hasNext()) {
			Map.Entry<String, Student> entry = entries.next();
			System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());
		}
		test2.myTest2();
	} 
}

  //构建原始数据
        ArrayList<Goods> list = new ArrayList();
        Goods goods1=new Goods("plum ", 2);
        list.add(goods1);
        list.add(new Goods("apple", 1));
        list.add(new Goods("banana", 2));
 
        //打印原始数据
        System.out.println("原始数据：");
        for(Goods goods : list){
            System.out.println(goods);
        }
        goods1.setGoodsId(444);//改变goods1的内容
        System.out.println("原始数据1：");
        for(Goods goods : list){
            System.out.println(goods);
        }