20145120 《Java程序设计》第3周学习总结

教材学习内容总结

基本类型与类类型的概念
在java里使用数组和字符串
封装的概念
在java定义函数
重载的概念
static的概念

因为程序很多所以我截取部分

猜数字

public class Guess {
    public static void main(String[] args) {
        Scanner console = new Scanner(System.in);
        int number = (int) (Math.random() * 10);
        int guess;

        do {
            System.out.print("猜数字（0 ~ 9）:");
            guess = console.nextInt();
        } while(guess != number);
        System.out.println("猜中了XD");
    }
}

使用BigDecimal

import java.math.BigDecimal;

public class DecumalDemo {
    public static void main(String[] args) {
        BigDecimal operand1 = new BigDecimal("1.0");
        BigDecimal operand2 = new BigDecimal("0.8");
        BigDecimal result = operand1.subtract(operand2);
        System.out.println(result);

        BigDecimal op1 = new BigDecimal("0.1");
        BigDecimal op2 = new BigDecimal("0.1");
        BigDecimal op3 = new BigDecimal("0.1");
        BigDecimal result2 = new BigDecimal("0.3");
        if(op1.add(op2).add(op3).equals(result2)) {
            System.out.println("等于 0.3");
        }
        else {
            System.out.println("不等于 0.3");
        }
    }
}

基本类型打包

public class IntegerDemo {
    public static void main(String[] args) {
        int data1 = 10;
        int data2 = 20;

        Integer wrapper1 = new Integer(data1);
        Integer wrapper2 = new Integer(data2);

        System.out.println(data1 / 3);
        System.out.println(wrapper1.doubleValue() / 3);
        System.out.println(wrapper1.compareTo(wrapper2));
    }
}

数组复制

class Clothes {
    String color;
    char size;
    Clothes(String color, char size) {
        this.color = color;
        this.size = size;
    }
}

public class Copy {
    public static void main(String[] args) {
        Clothes[] c1 = {new Clothes("red", 'L'), new Clothes("blue", 'M')};
        Clothes[] c2 = new Clothes[c1.length];
        for(int i = 0; i < c1.length; i++) {
            c2[i] = c1[i];
        }
        c1[0].color = "yellow";
        System.out.println(c2[0].color);    //浅层复制的结果

        Clothes[] c3 = {new Clothes("red", 'L'), new Clothes("blue", 'M')};
        Clothes[] c4 = new Clothes[c3.length];
        for(int i = 0; i < c3.length; i++) {
            Clothes c = new Clothes(c3[i].color, c3[i].size);
            c4[i] = c;
        }
        c3[0].color = "yellow";
        System.out.println(c4[0].color);    //深层复制的结果
    }
}

1到100

public class OneTo100 {
    public static void main(String[] args) {
        StringBuilder oneTo100 = new StringBuilder();
        for (int i = 1; i < 100; i++) {
            oneTo100.append(i).append('+');
        }
        System.out.println(oneTo100.append(100).toString());
    }
}

储蓄

import java.util.Scanner;

class CashCard {
    private String number;
    private int balance;
    private int bonus;

    CashCard(String number, int balance, int bonus) {
        this.number = number;
        this.balance = balance;
        this.bonus = bonus;
    }

    void store(int money) {
        if(money > 0) {
            this.balance += money;
            if(money >= 1000) {
                this.bonus++;
            }
        }
        else {
            System.out.println("储值是负的？你是来捣乱的吗？");
        }
    }

    void charge(int money) {
        if(money > 0) {
            if(money <= this.balance) {
                this.balance -= money;
            }
            else {
                System.out.println("钱不够啦！");
            }
        }
        else {
            System.out.println("扣负数？这不是让我储值吗？");
        }
    }

    int exchange(int bonus) {
        if(bonus > 0) {
            this.bonus -= bonus;
        }
        return this.bonus;
    }

    int getBalance() {
        return balance;
    }

    int getBonus() {
        return bonus;
    }

    String getNumber() {
        return number;
    }
}

public class CardApp {
    public static void main(String[] args) {
        Scanner console = new Scanner(System.in);

        CashCard card1 = new CashCard("A001", 500, 0);
        card1.store(console.nextInt());

        CashCard card2 = new CashCard("A002", 300, 0);
        card2.store(console.nextInt());

        CashCard card3 = new CashCard("A003", 1000, 1);
        card3.store(console.nextInt());

        System.out.printf("明细 (%s, %d, %d)%n",
                card1.getNumber(), card1.getBalance(), card1.getBonus());
        System.out.printf("明细 (%s, %d, %d)%n",
                card2.getNumber(), card2.getBalance(), card2.getBonus());
        System.out.printf("明细 (%s, %d, %d)%n",
                card3.getNumber(), card3.getBalance(), card3.getBonus());
    }
}