1.输出月份出现天数
Scanner scanner = new Scanner(System.in);
System.out.println("请输入想要查询的月份:");
String value = scanner .next();
int choice = Integer.valueOf(value);
if(choice == 1 ||choice == 3 ||choice == 5 ||choice == 7 ||choice == 8 || choice == 10 ||choice == 12) {
System.out.println("此月份共有：31天");
}else if(choice==2) {
System.out.println("此月份共有：28或者29天");
}else if(choice==4||choice == 6||choice == 9||choice == 11) {
System.out.println("此月份共有：30天");
}else {
System.out.println("请输入1~12月份:");
}
2.1到100的和
① int sum = 0;
int count = 0;
while(count <= 100) {
sum = sum +count;
count++;
}
System.out.println(sum);
②int sum=0;
for(int count = 1; count <= 100; count++) {
sum= sum+count ;
}
System. out. println(sum);
3.1~100能被3整除的数的和
① int i = 1;
int sum = 0;
while(i <=100) {
if(i%3==0) {
sum= sum +i ;
}
i++;
}
System.out.println(sum);
②int sum=0;
for(int count = 3; count <= 100; count=count+3) {
System . out. printIn( count) ;
sum= sum+count ;
}System . out. println(sum);
③int sum = 3;
int count = 0;
while(sum <= 100) {
count = count + sum;
sum = sum + 3;
}
System.out.println(count);
④ int i=0;
int sum1 =0;
do {
if(i%3==0) {
sum1= i +sum1;
}
i++;
}while(i<101);
System.out.println(sum1);
⑤ int sum2 = 0;
int count2 = 3;
do {
sum2 = sum2 + count2;
count2 = count2 + 3;
}while(count2<=100);
System.out.println(sum2);
⑥int i;
int sum=0;
for(i=1;i<=100;i++){
if( i%3==0){
sum=sum+i ;
System . out. print1n("i ="+ i);
System. out. println( sum);
⑦ int i;
int sum=0;
for(i=1;i<=100;i++){
if(i%3 == 0) {
//执行该语句时将结束循环
sum=sum+i ;
System. out. println("i = "+ i);
continue ;
/ /换成break试试
}System. out . println(sum);
4.for循环和if做能被2整除的数的和
int sum = 0 ;
for (int count = 1; count <= 100;count ++) {
if(count%2!=0) {
sum = sum +count;
}
}
System.out.println(sum);
5.输出1+2=3
int j1=1;
int j2=2;
int j3;
j3 = j1+j2;
System.out.println("1+2"+"="+j3);
6.商品管理系统
System.out.println("*******商品管理系统******");
System.out.println("1.查询所有商品");
System.out.println("2.根据商品编号查找图书");
System.out.println("3.购买图书");
System.out.println("4.取消图书");
System.out.println("5.查询购买情况");
System.out.println("6.退出系统");
System.out.println("*******商品管理系统****** \n1.查询所有商品\n2.根据商品编号查找图书\n3.购买图书\n4.取消图书\n5.查询购买情况\n6.退出系统");
System.out.println("*******商品管理系统******"+"\n1.查询所有商品"+"\n2.根据商品编号查找图书"+"\n3.购买图书"+"\n4.取消图书"+"\n5.查询购买情况"+"\n6.退出系统");
7.数据类型例子
int a=6;
double d=a;
System.out.println(d);
int num =(short)100L;
System.out.println(num);
System.out.println(20+30);
int c=20;
int b=30;
System.out.println(c-b);
System.out.println(c*10);
System.out.println(5/2);
System.out.println(5/0);
System.out.println(5/2.0);
System.out.println(5.0/2.0);
System.out.println(5.0/0.0);
System.out.println(-5.0/0.0);
System.out.println(10%3);
System.out.println(5.5%2);
System.out.println(5.5%0);
System.out.println('1'+1);
System.out.println('A'+1);
System.out.println("Hello"+"World");
String str2="Java";
System.out.println(str2+20);
System.out.println(str2+20+30);
System.out.println(str2+(20+30));
int e = 5;
System.out.println(e++);
System.out.println(e);
System.out.println(++e);
System.out.println(e);
System.out.println(e--);
System.out.println(e);
System.out.println(--e);
System.out.println(e);
a=4 ;
System.out.println(a--);
8.输出最大值
int p=10;
int u=20;
int max= p>u?p:u;
System.out.println("最大值："+max);
System.out.println(p>u?p:u);
9.字符、整数、小数、字符串
Scanner sc =new Scanner(System.in);
System.out.println("请输入一串字符信息:");
String strLine = sc.nextLine();
System.out.println("您输入的字符信息为："+strLine);
System.out.println("请输入一个整数:");
int i = sc.nextInt();
System.out.println("您输入的整数信息为："+i);
System.out.println("请输入一个小数:");
double d = sc.nextDouble();
System.out.println("您输入的一个小数为："+d);
System.out.println("请输入一个字符串信息:");
String str = sc.next();
System.out.println("您输入的字符串信息为："+str);
10.查询书籍业务
①Scanner scanner = new Scanner(System.in);
String value = scanner .next();
int choice = Integer.valueOf(value);
if(choice == 1) {
System.out.println("您选择了查询所有书籍的业务");
}
② Scanner scanner = new Scanner(System.in);
System.out.println("请输入想要查询的数字");
String value = scanner .next();
int choice = Integer.valueOf(value);
if(choice == 1) {
System.out.println("您选择了查询所有书籍的业务");
}else {
System.out.println("您的输入不正确，必须在1~6范围内!");
}
③Scanner scanner = new Scanner( System. in);
//获取用户对于菜 单的选择
String value = scanner .next( );
int choice = Integer . vaLueOf(value);
if(choice == 1) {
System. out . print1n("您选择了处理查询所有书籍的业务");
} else if( choice==2) {
System. out. println("您选择了处理按书籍编号查询");
} else if( choice==3) {
System. out . println("您选择了购买书籍");
} else {
System. out . println("您的输入不正确，必须在1~6范围内! ");
11.输入月份查询天数
①Scanner scanner = new Scanner(System.in);
System.out.println("请输入想要查询的数字");
String value = scanner .next();
int choice = Integer.valueOf(value);
if(choice == 1) {
System.out.println("1月份共有：31天");
}else if(choice ==2) {
System.out.println("2月份共有：28或者29天");
}else if(choice ==3) {
System.out.println("3月份共有：31天");
}else if(choice ==4) {
System.out.println("4月份共有：30天");
}else if(choice ==5) {
System.out.println("5月份共有：31天");
}else if(choice ==6) {
System.out.println("6月份共有：30天");
}else if(choice ==7) {
System.out.println("7月份共有：31天");
}else if(choice ==8) {
System.out.println("8月份共有：31天");
}else if(choice ==9) {
System.out.println("9月份共有：30天");
}else if(choice ==10) {
System.out.println("10月份共有：31天");
}else if(choice ==11) {
System.out.println("11月份共有：30天");
}else if(choice ==12) {
System.out.println("12月份共有：31天");
}else {
System.out.println("请输入1~12月份:");
}
②Scanner scanner = new Scanner(System.in);
int month;
System.out.println("请输入月份：");
month = scanner.nextInt();
switch(month) {
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
System.out.println("此月份共有：31天");
break;
case 2:
System.out.println("2月为28或者29天");
break;
case 4:
case 6:
case 9:
case 11:
System.out.println("4月份共有：30天");
break;
}
12.1—100奇数和
①int sum = 0 ;
for (int count = 1; count <= 100;count = count +2) {
sum = sum + count;
}
System.out.println(sum);
② int i = 0;
int sum = 0;
while(i <= 100) {
sum= i + sum;
i = i + 3;
}
System.out.println(sum);
13.录入5门成绩
① int sum =0;
int j;
for (int i = 1;i<=5;i++) {
System.out.println("第"+i+"门的成绩:"+j);
}if(j<0) {
System.out.println("录入错误");
break;
}
System.out.println(j);
sum+=j;
}System.out.println(sum);
②//循环录入某学生5门课的成绩并计算总分，如果某分数录入为负，停止录 入并提示录入错误。
int sum=0;
for(int i=0;i<5;i++) {
//输入纳入循环
Scanner scanner = new Scanner(System. in);
String value = scanner .next();
int choice = Integer . value0f(value);
if(choice<0)
{
System. out. println( "输入错误");
sum=0 ;
break;
}
sum=sum+choice;
}
System.out.println(sum/5.0);//平均值
14.图书目录循环版
for(;;) {
System. out . println("********商品管理系统********");
System. out . println("1.查询所有商品");
System. out . println("2.根据商品编号查找图书");
System. out . println("3.购买图书");
System. out . println("4.取消购买");
System. out . println("5.借阅图书");
System. out . println("0.退出系统");
Scanner scanner = new Scanner(System.in) ;
String value = scanner.next( );
int choice = Integer . valueOf(value );
if(choice==0){
System. out . println("退出系统");
break;
}
if(choice==1) {
System. out. println("进行查询");
}
if(choice==2) {
System. out. println("进行查找");
}
if(choice==3) {
System. out . println("进行购买");
}
if(choice==4) {
System. out. println("取消购买");
}
if(choice==5) {
System. out. println("借阅图书");
}
15.for循环
①for (int i= 1;i<=720;i++) {
System.out.println("孙猴子72变"+"第"+i+"变");
}System.out.println("孙猴子完成72变");
②for(int i=e;i<18;i++) {
System. out. print1n("练习降龙18掌,第"+(i+1)+"掌!");
}System. out . print1n("恭喜练成降龙18掌! ");
③int sum=0;
for(int i=1;i<=180000;i++) //循环18次
sum=3*i;
//System.out.println("练习降龙18掌，第"+i+"掌!");
//18万次的显示器慢, 18万次的乘法很快
System. out.println("恭喜练成降龙18掌! ");
16.输出1~10++
int count;
for (count = 1 ; count<=10;count++) {
System.out.println(count);
//输出结果为1~10
}
System.out.println(count);
//输出结果为11
17.do while循环
①do {
System. out . println( count);
/ /迭代语句
count++ ;
}while(count < 10);
System. out. println( "循环结束! ");
②int count = 1, sum=0;
do {
sum= sum+count ;
/ /迭代语句
count++ ;
}while(count <=100);
System . out. println(sum);
18.输出到7结束循环
inti;
for(i=1;i<=10;i++){
if(i%7 == 0) {
//执行该语句时将结束循环
break ;
}
System. out. println("i =”+ i);
}
System . out. print1n( "循环中断:i = " + i);
19.水仙花数
//外层循环，outer作 为标识符
outer :
for(int a=1;a<=9;a++){
//嵌套的中间层，middle作为标识符
middle :
for(intb=0;b<=9;b++){
//最内层的循环
for(int c=0;c<=9;c++){
if(a*a* a+b*b*b+c*c*c==100*a+10*b+c) {
System. out. println("水仙花数: " + (100 * a+10*b+c));
//忽略outer标签 所指定的循环中本次循环所剩下语句
continue outer ; } } } }
20.乘法表
//外层循环
for(inti=1;i<=9;i++){
//内层循环
for(intj=1;j<=i;j++){
System. out.print(i +”*”+j+="+(i*j));
System. out. print("\t");
System. out . print1n();
}
21.构造方法以及私有
package unit3.task01;
public class Book {//类名Book
//属性
private String bid;
private String name;
private String author;
private int number;//私有的
private String category;
public Book() {//构造方法
// TODO Auto-generated constructor stub
}
public Book(String bid,String name,String author,int number,String category) {//构造方法， 带参数5个，重载
// TODO Auto-generated constructor stub
this.bid=bid;//传入的bid的值给了新建对象
this.name=name;//后面的是参数name，前面的是属性this
this.author=author;
this.number=number;
this.category=category;
}
public String toString() {
return "输出:"+ this.bid+this.name+this.author+this.number+this.category;
}
public String getbid() {
return this.bid;
}
public int getNumber() {
return this.number;
}
public void setNumber(int num) {
if(num>0) {
this.number=num;
System.out.println("设置成功");
}else {
System.out.println("数值小于0，设置不成功");
}
}
public String getAuthor() {
return this.author;
}
public String getName() {
return this.name;
}
public String getCategory() {
return this.category;
}
public static void main(String[] args) {
// TODO Auto-generated method stub
/* Book b1=new Book();//调用了构造方法，使用了无参数的构造方法
b1.bid ="b01";
b1.name="三国演义";
b1.author="罗贯中";
b1.number=40;
b1.category="小说";
System.out.println(b1);*/
Book b2=new Book("b02","JAVA","robort",20,"编程");//调用了构造方法，使用了有参数的构造方法
b2.setNumber(40);
b2.setNumber(-2);
System.out.println(b2);
System.out.println(b2.getAuthor());
}
}
22.变量作用域
package unit3.task01;
public class Book1 {
private static String name = "类别";//类级
private int i;//对象实例级
{//属性块，在类初始化属性时候运行
int j = 3;//块级
}
public void test1() {
// TODO Auto-generated constructor stub
int j = 4;//方法级
if(j==4) {
int k = 5;//块级
}
//这里不能访问块级的变量，块级变量只能在块内部访问
System.out.println("name="+name+",i="+i+",j="+j);
}
public static void main(String[] args) {
// TODO Auto-generated method stub
Book1 t = new Book1();
t.test1();
Book1 t2 = new Book1();
}
}
23.二维数组
//假定班级有60名同学， 有三门课程:语文、数学、英语(成绩在40-100之间)计算三门课程的平均分
扫一扫
2万+
到【灌水乐园】发言
