1.bank类
package com.yfs.javase;
//类封装
public class BankCard {
//属性
int balance;//默认0 实例变量 分配给每个对象一个
//String name;
// 方法 存钱
public void saveMoney(int money) {
if(money < 0) {
System.out.println("非法操作...");
return;
}
System.out.println("向账户存入" + money +"元...");
balance += money;
}
//取钱 调用时传入参数
public void drawMoney(int money) {
//验证余额
if(balance < money) {
System.out.println("账户余额不足...");
return; //终止方法调用
}
System.out.println("从账户取出" + money + "元...");
balance -= money;
}
}
2.测试
package com.yfs.javase;
public class CardTest {
public static void main(String[] args) {
// BankCard bc1 = null;//声明引用
// bc1 = new BankCard();//创建对象
BankCard bc1 = new BankCard();
System.out.println("银行卡余额：" + bc1.balance);
bc1.drawMoney(200);//调用对象方法
bc1.saveMoney(5000);
bc1.drawMoney(500000);
bc1.drawMoney(500);
bc1.saveMoney(-500);
System.out.println("银行卡余额：" + bc1.balance);
}
}
3.测试1
package com.yfs.javase;
public class CardTest2 {
public static void main(String[] args) {
BankCard bc1 = new BankCard();
System.out.println("银行卡余额：" + bc1.balance);
bc1.saveMoney(5000);
bc1.drawMoney(500);
System.out.println("银行卡余额：" + bc1.balance);
BankCard bc2 = new BankCard();
System.out.println("银行卡余额：" + bc2.balance);
bc2.saveMoney(3000);
System.out.println("bc2银行卡余额：" + bc2.balance);
System.out.println("bc1银行卡余额：" + bc1.balance);
}
}
4.测试2
package com.yfs.javase;
public class CardTest3 {
public static void main(String[] args) {
BankCard bc1 = new BankCard();
bc1.saveMoney(5000);
bc1.drawMoney(500);
System.out.println("银行卡余额：" + bc1.balance);
BankCard bc2 = new BankCard();
bc2.saveMoney(3000);
System.out.println("bc2银行卡余额：" + bc2.balance);
bc2.drawMoney(5000);
bc2.balance = 10000;//修改余额 不安全操作
bc2.drawMoney(5000);
System.out.println("bc2银行卡余额：" + bc2.balance);
}
}
1.1bank类
package com.yfs.javase.update;
//类封装
public class BankCard {
//属性 private 属性私有 只能在当前类中访问
private int balance;// 实例变量 分配给每个对象一个
private int password;
// 方法 存钱
public void saveMoney(int money) {
if(money < 0) {
System.out.println("非法操作...");
return;
}
System.out.println("向账户存入" + money +"元...");
balance += money;//在方法中访问
}
//取钱 调用时传入参数
public void drawMoney(int money) {
//验证余额
if(balance < money) {
System.out.println("账户余额不足...");
return; //终止方法调用
}
System.out.println("从账户取出" + money + "元...");
balance -= money;
}
//通过访问balance属性方法 不能修改
public void getBalance () {
System.out.println("账户余额：" + balance);
}
}
2.1测试
package com.yfs.javase.update;
public class CardTest3 {
public static void main(String[] args) {
BankCard bc1 = new BankCard();
bc1.saveMoney(5000);
bc1.drawMoney(50000);
// bc1.balance = 100000000;//编译出错
// System.out.println("银行卡余额：" + bc1.balance);//私有属性不能访问
bc1.getBalance();
// bc1.password;
}
}
3.1方法重载条件
package com.yfs.javase.update;
import java.util.Random;
public class Demo2 {
// public int add(int a, int b) {
// return a + b;
// }
//变量名称不能成为重载条件
// public int add(int c , int d) {
// return c + d;
// }
public double add(int a , double b) {
return a + b;
}
//返回值类型不能成为重载条件
public long add( int a, int b) {
return a + b;
}
public static void main(String[] args) {
Demo2 d1 = new Demo2();
long val = d1.add(1,6);
}
}
4.1方法重载示例
package com.yfs.javase.update;
public class OverRideDemo {
//方法的重载 方法使用相同的名字
public int add (int a, int b) {
return a + b;
}
public int add (int a , int b, int c) {
return a + b + c;
}
public double add( double a, double b) {
return a + b;
}
public static void main(String[] args) {
//创建对象
OverRideDemo od = new OverRideDemo();
int val = od.add(3,5);
System.out.println("add(3,5) = " + val);
val = od.add(3,5,8);//根据调用时传入参数个数 类型匹配对应方法
System.out.println("add1(3,5,8) = " + val);
double result = od.add(3.14, 2.71);
System.out.println("add(3.14, 2.71) = " + result);
}
}