Java：封装（对于含构造器的成员变量的调用和限制）

 

1）随便查看个人的年纪，工资等隐私，并对设置的年龄进行合理验证，年龄 合理就设置，否则输出error,工资和年龄不能直接查看，name 的长度在2-4之间

要求使用构造器对各属性进行初始化，同时也要对初始化的变量范围进行验证

package ex;
public class ex2 {
	public static void main(String args[]) {
	person t = new person(4,46,"egd");
	System.out.println(t.info());
	}
}
class person{
	private int age;
	private double salary;
	public String name;
	public person(int age,double salary,String name) {
		setage(age);//将Set方法写到构造器中，这样就能验证
		setname(name);
		setsalary(salary);
	}
	public void setage(int age)
	{
		if(age>18&&age<100)
			this.age=age;
		else 
			System.out.println("age is erro");
	}
	public void setname(String name) {
		if(name.length()>2&&name.length()<4)
			this.name=name;
		else 
			System.out.println("name is error");
	}
	public void setsalary(double salary) {
		this.salary=salary;
	}
	public String getname() {
		return name;
	}
	public int getage() {
		return age;
	}
	public double getsalary()
	{
		return salary;
	}
	public String info() {
		return "name="+name+"\t"+"age="+age+"\t"+"salary="+salary;
	}
}

输出结果：age is erro

name=egd        age=0        salary=46.0

 疑惑：这个age既然不符合题意为啥输出还是0，是因为初始化之后赋给它一个默认值吗

2）

package ex;
public class accounttest {
	public static void main(String args[]) {
		account a =new account("1",3,"12345");
		System.out.print(a.info());
	}

}
class account{
	//为了封装，将三个属性均设置为private
	private String name;
	private double balance;
	private String key ;
	//设置两个构造器，一个空一个含参
	//两个构造器都可以用，用空的时候，接收就get方法，用含参的也行
	public account() {
	}//空构造器
	public account(String name,double balance,String key) {
		setname(name);//让方法生效
		setbalance(balance);
		setkey(key);
	}
	public void setname(String name) {
		if(name.length()==2||name.length()==3||name.length()==4) 
			this.name=name;
		else
			this.name="无名";
	}
	public void setbalance(double balance) {
		if(balance > 20)
			this.balance=balance;
		else
			this.balance=-1;
	}
	public void setkey(String key) {
		if(key.length()==6)
			this.key=key;
		else 
			this.key="0000000";
	}
	public String getname() {
		return name;
	}
	public double getbalance() {
		return balance;
	}
	public String getkey() {
		return key;
	}
	public String info() {
		return "name="+name+"\t"+"balance="+balance+"\t"+"key="+key;
	}
}

输出结果：

name=无名    balance=-1.0    key=0000000