Java 类的继承 A extends B

Acount 类

public class Acount {
    
    
    private String ac;
    private String balance;
    public Acount() {
    
    
    }
    public Acount(String ac, String balance) {
    
    
        this.ac = ac;
        this.balance = balance;
    }

    public String getAc() {
    
    
        return ac;
    }

    public void setAc(String ac) {
    
    
        this.ac = ac;
    }

    public String getBalance() {
    
    
        return balance;
    }

    public void setBalance(String balance) {
    
    
        this.balance = balance;
    }
}

CreditAcount 类

public class CreditAcount extends Acount {
    
    
    private String credit;

    public CreditAcount() {
    
    
    }

    public CreditAcount( String credit) {
    
    
        this.credit = credit;
    }

    public String getCredit() {
    
    
        return credit;
    }

    public void setCredit(String credit) {
    
    
        this.credit = credit;
    }

    public static void main(String[] args) {
    
    
        CreditAcount creditAcount = new CreditAcount();
        creditAcount.setAc("123456789");
        creditAcount.setBalance("999999999");
        creditAcount.setCredit("888888888");
        System.out.println(creditAcount.getAc()+creditAcount.getBalance()+creditAcount.credit);
        System.out.println("账户和余额的set和get是类CreditAcount从类Acount中继承来的");
    }
}

虽然Acount中ac和balance是私有的但是他们的get和set方法是公有的，所以CreditAcount类可以继承过来直接使用因此可以在CreditAcount类中调用set和get方法来修改Acount类中的ac和balance属性的值。
在Java类中除了私有属性和构造方法不能被继承其他的都可以被继承。