java基础3

1 输入内容 ：
Scanner scanner = new Scanner(System.in);
System.out.print("age: "); //print在同一行显示，println下一行显示
byte age = scanner.nextByte(); // 浮点数：nextFloat,nextDouble,字符串nextLine(),前后对应
System.out.println("your age is " + age );

**2:**mortgage calculater
// 此code未添加输入有误时的对应机制
public class Main {

public static void main(String[] args) {
    byte month =12;
    byte percent = 100;
    Scanner scanner = new Scanner(System.in);

    System.out.print("Principal: ");
    int principal = scanner.nextInt();

    System.out.print("Annual Interest Rate: ");
    float rate_month = scanner.nextFloat()/month/percent;   //将常数变量化

    System.out.print("Period (Year): ");
    byte period = scanner.nextByte();

    double res = principal*(rate_month*(Math.pow(1+rate_month,period*12))/(Math.pow(1+rate_month,period*month)-1));
    String res1 = NumberFormat.getCurrencyInstance().format(res);
    System.out.print("mortgage: " +res1);
}

}

3：逻辑运算符
与 &&
或 ||
非 ！

条件语句： java
if（）{
…
}
else if ()
…
else ()
…
python if : elif : else:

4: 代码简化
public static void main(String[] args){

int income = 12_000;
String className;
if (income>10_000)
	className = "first";
else
	className="second"
}

可改变为：(赋初值，保留一个条件）
int income = 12_000;
String className = “second”;
if (income>10_000)
className = “first”;
进一步： 三元运算符
String className = income >10_000？" first"：“second”

5: switch case

String role = “admin”;
switch (role){
case “admin”:
System.out.println(“admin”);
break;
case “moderate”:
System.out.println(“moderate”);
break;
default:
System.out.println(“nothing”);
break;
}
//由于role 为字符串格式，case后面直接跟字符串
当role 为int 格式，case后面可直接写整形数字