定义People类:

public class People {
	private String name;
	private String sex;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getSex() {
		return sex;
	}
	public void setSex(String sex) {
		this.sex = sex;
	}
}

定义Hospital类:

public class Hospital {
	private People a;

	public People getPeople() {
		return a;
	}

	public void setPeople(People a) {
		this.a = a;
	}
	
	public void changePeopleInfo(){
		a.setName("小青");
		a.setSex("女");
	}
}

  main方法:

public static void main(String[] args) {  
		People a = new People();
		a.setName("张三");
		a.setSex("男");
		Hispital b =new Hispital();
		b.setA(a);
		b.setAInfo();
		System.out.println(a.getName()+"--"+a.getSex());
	}

  程序解读:

一个人姓名:张三,性别:男; 把这个人放进医院,改造后变为小青,性别:女.