Java学习记录(补充一(以习题为主:判断,循环语句))
习题1:取一个四位数,求各个位数数字的和
package Day2;import java.util.Scanner;
public class Demo01 {
public static void main(String[] args){
Scanner in = new Scanner(System.in);
System.out.println("请输入你的卡号");
int cardNum = in.nextInt();
// 1234
int i1 = cardNum % 10;
int i2 = cardNum/10%10;
int i3 = cardNum/100%10;
int i4 = cardNum/1000;
int result = i1+i2+i3+i4;
System.out.println("会员卡号之和:"+result);
}
}
结果图:
基本数据类型与包装类之间的转换
package Day2;public class Demo021 {
public static void main(String[] args) {
// 基本数据类型转换为包装类的方法 valueOf()
byte b = 21;//基本数据类型
Byte b2 = Byte.valueOf("21"); //包装数据类型（装箱）
System.out.println(b2.MAX_VALUE);
System.out.println(b2.MIN_VALUE);
System.out.println(b2.SIZE);
short s = 123;//基本数据类型
Short s2 = Short.valueOf("123");
System.out.println(s2.MAX_VALUE);
System.out.println(s2.MIN_VALUE);
System.out.println(s2.SIZE);
// int--->Integer valueOf(装箱)可以使用包装类的方法
Integer i1 = Integer.valueOf(5);
// Integer--->int xxxValue(拆箱)
int i2 = i1.intValue();
// 字符串--->基本数据类型 parseXXX
int i3 = Integer.parseInt("123");
System.out.println(i3);
boolean b1 = Boolean.parseBoolean("1");
System.out.println(b1);
short s3 = Short.parseShort("123");
System.out.println(s3);
// 基本数据类型--->字符串 String.valueOf()
String s4 = String.valueOf(1);
System.out.println(s4);
}
}
转换总结
package Day2;public class Demo022 {
public static void main(String[] args) {
// 基本数据类型 ---> 包装类 valueOf(三种)
Integer i1 = Integer.valueOf(23);
Integer i2 = new Integer(24);
Integer i3 = 25;
// 包装类 -----> 基本数据类型 xxxValue
int i4 = i1.intValue();
int i5 = i2;
// String ---- >基本数据类型
int i6 = Integer.parseInt("123");
System.out.println(i6);
// 基本数据类型 ----> String
String s1 = String.valueOf(123);
String s2 = Integer.toString(123);
System.out.println(s2);
float f = 12.5F;
// 强制类型转换会损失精度
int ccy = (int)f;
System.out.println(ccy);
System.out.println(6.0%4);
}
}
结果图;
习题2:(if-else语句)
package Day2;import java.util.Scanner;
public class Demo03 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("请输入你的成绩");
int score = input.nextInt();
if (score > 90) {
System.out.println("A");
} else if (score >= 80) {
System.out.println("B");
} else if (score >= 60) {
System.out.println("C");
} else {
System.out.println("D");
}
}
}
结果图:
习题3:(switch语句)
package Day2;import java.util.Scanner;
public class Demo04 {
public static void main(String[] args) {
System.out.println("商品列表:");
System.out.println("1:绿茶,三元");
System.out.println("2:冰红茶,三元");
System.out.println("3:脉动,五元");
System.out.println("4:咖啡,五元");
System.out.println("5:酸奶,六元");
Scanner input = new Scanner(System.in);
System.out.println("请输入你要购买的商品的序号");
int num = input.nextInt();
switch(num){
case 1 :
System.out.println("您买的绿茶,请支付三元");
break;
case 2 :
System.out.println("您买的冰红茶,请支付三元");
break;
case 3 :
System.out.println("您买的脉动,请支付五元");
break;
case 4 :
System.out.println("您买的咖啡,请支付五元");
break;
case 5 :
System.out.println("您买的酸奶,请支付六元");
break;
default:
System.out.println("您输入的商品序号有误");
}
}
}
结果图:
习题4:(do-while语句嵌套if语句)
package Day2;import java.util.Scanner;
public class Demo05 {
public static void main(String[] args) {
System.out.println("欢迎进入我行我素管理系統");
System.out.println("------------------");
Scanner scanner = new Scanner(System.in);
do{
System.out.println("请输入会员号(四位整数)");
int cardNo = scanner.nextInt();//.nextInt:接收整形数据
System.out.println("请输入会员生日[月/日<用两位数表示>]");
String birthDay = scanner.next();//.next:接收字符串数据
System.out.println("请输入积分");
int score = scanner.nextInt();
if(cardNo>999&&cardNo<10000){
System.out.println("会员卡号为"+cardNo);
System.out.println("会员生日为"+birthDay);
System.out.println("会员积分为"+score);
System.out.println("信息录入成功");
break;
}else{
System.out.println("登入信息失败");
}
}while(true);
}
}
结果图;
习题5:(do-while语句嵌套if-else语句)
package Day2;import java.util.Scanner;
public class Demo06 {
public static void main(String[] args) {
System.out.println("请输入会员积分");
Scanner input = new Scanner(System.in);
boolean goOn = false;
do {
int cardNo = input.nextInt();
if (cardNo < 2000) {
System.out.println("该会员可享受九折");
} else if (cardNo < 4000) {
System.out.println("该会员可享受八折");
} else if (cardNo < 8000) {
System.out.println("该会员可享受七折");
} else {
System.out.println("该会员可享受六折");
}
System.out.println("是否继续(y/n)?");
String result = input.next();
if (result.equals("y")) {
goOn = true;
System.out.println("请再次输入积分");
} else {
goOn = false;
}
} while (goOn);
}
}
结果图:
习题6:(do-while语句同时嵌套switch和if语句)
package Day2;import java.util.Scanner;
public class Demo07 {
public static void main(String[] args) {
System.out.println("请选择想要购买的商品编号");
System.out.println("1.T恤\t2.网球鞋\t3.网球拍");
Scanner scanner = new Scanner(System.in);
boolean goOn = false;
do {
System.out.println("请输入想要购买的商品编号");
int node = scanner.nextInt();
System.out.println("请输入想要购买的数量");
int num = scanner.nextInt();
int sum1 = 245;
int sum2 = 570;
int sum3 = 300;
switch (node) {
case 1:
System.out.println("T恤$245.0" + "\t数量" + num + "\t合计$" + sum1 * num);
break;
case 2:
System.out.println("网球鞋$570.0" + "\t数量" + num + "\t合计$" + sum2 * num);
break;
case 3:
System.out.println("网球拍$300.0" + "\t数量" + num + "\t合计$" + sum3 * num);
break;
default:
break;
}
System.out.println("是否要继续(y/n)?");
String result = scanner.next();
if (result.equals("y")) {
goOn = true;
} else {
goOn = false;
int all = (sum1 * num + sum2 * num + sum3 * num);
System.out.println("折扣:0.8");
System.out.println("实付金额:" + all * 0.8);
System.out.println("应付金额:" + all);
System.out.println("找钱:" + all * 0.2);
}
} while (goOn);
System.out.println("欢迎下次光临哦~小肥羊");
}
}
结果图:
习题7:(do-while语句嵌套while语句(内涵if语句);外含if语句;注意语句中Continue和break的用法)
package Day2;import java.util.Scanner;
public class Demo08 {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
String password = "111111";//银行卡密码
int passwordNum = 0;//密码输入次数
boolean passWordPass = false;//密码在三次以内通过
do {
System.out.println("请输入密码：");
if(!scanner.next().equals("111111")){
passwordNum++;
continue;
}
passWordPass = true;
System.out.println("请输入取款金额：");
int money = scanner.nextInt();
while(money > 0){
if(money<=1000 && money%100==0){
System.out.println("您取了" +money+ "元");
System.out.println("交易完成，请取卡！");
break; //完成交易，退出
}else{
System.out.print("您输入金额的金额不合法，请重新输入：");
money = scanner.nextInt();
continue; //继续让用户输入金额
}
}
} while (passwordNum < 3 && !passWordPass);
if(!passWordPass){
System.out.println("密码输入错误三次，请取卡！");
}
}
}
结果图:
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