# java第二周上机练习

1．编写一个程序，定义圆的半径,求圆的面积.

public class Homework0312_01{
public static void main(String[] args){
mianJi();
}
public static double banJing(){
System.out.println("请输入半径的长");
java.util.Scanner s = new java.util.Scanner(System.in);
double banJing = s.nextDouble();
while(banJing < 0){
System.out.println("半径长度不能小于零，请重新输入");
banJing = s.nextDouble();
}
return banJing;
}
public static double mianJi(){
double banJing = banJing();
double mianJi = banJing * banJing * 3.14;
System.out.println("面积是" + mianJi);
return mianJi;
}
}


2．华氏温度和摄氏温度互相转换，从华氏度变成摄氏度你只要减去32，乘以5再除以9就行了，将摄氏度转成华氏度，直接乘以9，除以5，再加上32即行。

public class Homework0312_02{
public static void main(String[] args){
huaZhuanShe();

sheZhuanHua();
}
public static double huaShiDu(){
System.out.println("请输入华氏度");
java.util.Scanner s = new java.util.Scanner(System.in);
double hua = s.nextDouble();
while(hua < -459.67){
System.out.println("不能低于绝对零度，请重新输入");
hua = s.nextDouble();
}
return hua;
}
public static double sheShiDu(){
System.out.println("请输入摄氏度");
java.util.Scanner s = new java.util.Scanner(System.in);
double she = s.nextDouble();
while(she < -273.15){
System.out.println("不能低于绝对零度，请重新输入");
she = s.nextDouble();
}
return she;
}
public static void huaZhuanShe(){
double hua = huaShiDu();
double she = (hua - 32) * 5 / 9;
System.out.println(hua + "华氏度可转化为" + she + "摄氏度");
return;
}
public static void sheZhuanHua(){
double she = sheShiDu();
double hua = (she * 9 / 5) + 32;
System.out.println(she + "摄氏度可转化为" + hua + "华氏度");
return;
}
}


3．已知a,b均是整型变量，写出将a,b两个变量中的值互换的程序。

public class Homework0312_03{
public static void main(String[] args){
int a = 5;
int b = 8;
int c = 0;
c = a;
a = b;
b = c;
System.out.println("a由5变为" + a + "\tb由8变为" + b);
}
}


4．定义一个任意的5位整数，将它保留到百位，无需四舍五入

public class Homework0312_04{
public static void main(String[] args){
int num = num();
int num2 = (num / 100) * 100;
System.out.println("保留到百位后等于" + num2);
}
public static int num(){
System.out.println("请输入五位整数");
java.util.Scanner s = new java.util.Scanner(System.in);
int num = s.nextInt();
while(num < 10000 || num > 99999){
System.out.println("您输入的不是五位数，请重新输入");
num = s.nextInt();
}
return num;
}
}


5．输入一个0～1000的整数，求各位数的和，例如345的结果是3+4+5＝12

public class Homework0312_05{
public static void main(String[] args){
xiangJia();
}
public static int shuRu(){
System.out.println("请输入一个0~1000的整数");
java.util.Scanner s = new java.util.Scanner(System.in);
int num = s.nextInt();
while (num < 0 || num > 1000){
System.out.println("您输入的数据有误，请重新输入");
num = s.nextInt();
}
return num;
}
public static void xiangJia(){
int num = shuRu();
int sum = 0;
for (int a = 0 ; num > 0; num /= 10){
a = num % 10;
sum += a;
}
System.out.println("该整数每位相加的和是" + sum);
return;
}
}


6．定义一个任意的大写字母A~Z，转换为小写字母（知识点：变量和运算符综合应用）

public class Homework0312_06{
public static void main(String[] args){
char daXie = 'A';
System.out.println("由" + daXie + "转化为" + (char)(daXie + 32));
char xiaoXie = 'a';
System.out.println("由" + xiaoXie + "转化为" + (char)(xiaoXie - 32));
}
}


posted @ 2021-03-12 10:06  音无彩名  阅读(58)  评论(0编辑  收藏  举报