java/w3/BankAccount.java

public class BankAccount {
	private final int accountNumber;
	private String ownerName;
	private double balance;

	public BankAccount(int accountNumber,String ownerName){
		this.balance=0.0;
		this.accountNumber=accountNumber;
		this.ownerName=ownerName;
	}

	public void setOwnername(String ownerName) {
		this.ownerName=ownerName;
	}

	public void addBalance(double add){

		if (add > 0.0){
			this.balance+=add;
			System.out.println("成功更新余额为"+balance+"元");
		} else {
			System.out.println("存款失败，金额小于零");
		}
	}

	public void takeBalance(double take){
		if (take > 0.0 && take <=balance){
			this.balance-=take;
			System.out.println("成功更新余额为"+balance+"元");
		} else {
			System.out.println("取款失败，金额不足");
		}
	}
	public void lookBalance(){
		System.out.println("余额为"+balance);
	}
    public static void main(String[] args) {
        BankAccount myAccount = new BankAccount(1001, "张三");
        
        myAccount.lookBalance(); // 输出: 余额为 0.0
        
        myAccount.addBalance(500.0); // 输出: 成功存入... 余额 500.0
        
        myAccount.takeBalance(200.0); // 输出: 成功取出... 余额 300.0
        
        myAccount.takeBalance(400.0); // 输出: 取款失败... (余额不足)
        
        myAccount.addBalance(-50.0);  // 输出: 存款失败... (金额小于零)
    }
}