java课堂作业（六）

思路分析：直接按照题目写

class Account {
    private String id;
    private int password;
    private String name;
    private String personId;
    private String email;
    private double balance;
    
    public Account(){
        id = "1234567890123456";
        password = 123456;
        name = "张三";
        personId = "123456789012345678";
        email = "12345678@gmail.com";
        balance = 0.0;
    }
    
    public Account(String id,int password,String name,
            String personId,String email,double balance){
        this.id = id;
        this.password = password;
        this.name = name;
        this.personId = personId;
        this.email = email;
        this.balance = balance;        
    }
    
    public double deposit(double cun){
        return balance+=cun;
    }
    
    public double withdraw(double qu){
        return balance-=qu; 
    }
}

在做这道题目的时候，发现了一个特别有意思的问题

class A{
    public String name;
    public void setName(String name){
        this.name = name;        
    }
    public String getName(){
        return name;
    }
}
class ZhiChuanDiTest {
    public static void call(A a1) {
        A a2 = new A();
        a2.setName("cba");
        a1.setName("abc");
        a1 = a2 ;
        }

    public static void main(String[] arg) {
        A test = new A();
        call (test) ;
        System.out.println("test"+test.getName());
        } 
}

运行结果：

原因分析：

在call()方法中，我们new了一个对象a2，名字设置成cba，然后把a2的引用传递给了参数引用a1（地址值而非真正引用），a1和a2现在的地址值相同，指向同一块内存区域。

我们在main方法中new了一个test，然后用test调用call函数，这个过程中，test引用中保存的地址值传递给形参a1，a1和test指向同一块内存区域，把name设置成了abc

最后a1放弃指向test那一块内存 转而指向了 a2 的那一块 内存 ，所以 最后输出 test 的 name ，abc

只影响了a1 而没有影响到 test

思路分析：照要求写

class BJMiFen{
    private String mm;
    private int fl;
    private boolean dt;
    
    public BJMiFen(){
        mm = "酸";
        fl = 1;
        dt = true;
    }
    
    public BJMiFen(String mm,int fl,boolean dt){
        this.mm = mm;
        this.fl = fl;
        this.dt = dt;        
    }
    
    public void set(String mm,int fl,boolean dt){
        this.mm = mm;
        this.fl = fl;
        this.dt = dt;
    }
    
    public String toString(){
        String a;
        if(dt==true){
            a = "带汤";
        }else{
            a = "不带汤";
        }
        return "面码:"+mm+"  "+"分量:"+fl+"两"+"  "+"是否带汤:"+a;
    }
    
}
public class BJMiFenTest {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        BJMiFen b1 = new BJMiFen();
        b1.set("酸辣", 5, true);
        System.out.println(b1.toString());
    }

}

输出：