流程控制
流程控制
scanner对象
next
package Study;
import java.util.Scanner;
public class Scan {
public static void main(String[] args) {
Scanner scanner= new Scanner(System.in);
System.out.println("使用next方式接收:");
//判断用户有没有输入字符串
if(scanner.hasNext()){
//使用next方式接收
String str = scanner.next();
System.out.println("输出内容为:" +str);
}
//凡是输入IO流的类如果不关闭会一直占用资源,要及时关闭
scanner.close();
}
}
遇到空格即断!
nextline
package Study;
import java.util.Scanner;
public class Scan {
public static void main(String[] args) {
//从键盘接收数据
Scanner scanner= new Scanner(System.in);
System.out.println("使用next方式接收:");
//判断用户有没有输入字符串
if(scanner.hasNextLine()){ //判断是否还有输入
//使用nextLine方式接收
String str = scanner.nextLine();
System.out.println("输出内容为:" +str);
}
scanner.close();
}
}
遇到空格不断!
计算平均值 总和实例
package Study;
//计算输入多个数据的平均值以及总和
import java.util.Scanner;
public class Scan3 {
public static void main(String[] args) {
double sum = 0.0;
double m=0;
Scanner scanner = new Scanner(System.in);
System.out.println("请输入数字:");
while(scanner.hasNextDouble()){ //注意这里是nextDouble()
double s = scanner.nextDouble();
m++;
sum+=s;
}
System.out.println("数字总和为:"+sum);
System.out.println("平均值为:"+(sum / m));
scanner.close();
}
}
循环
java基本结构 顺序结构
选择结果
if:
package Study;
import java.util.Scanner;
public class Demo05 {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in );
System.out.println("请输入成绩:");
int score = scanner.nextInt();
if(score>60){
System.out.println("及格!");
}
else{
System.out.println("不及格!");
}
}
}
swich选择结构:
break 虽然可选,但是如果不加,就可能会导致case 穿透现象,即将其后的判断一同输出
package Study;
public class Demo06 {
public static void main(String[] args) {
String name = "小伟";
switch (name){
case "小伟":
System.out.println("牛逼!"); break;
case "阿伟":
System.out.println("阿伟已经死了!"); break;
}
}
}
循环结构
while:
do while:
for循环:
print 和println的区别:
print输出不换行 println输出会换行
0-1000之间能被5整除的数,每三个换行
package Study;
//注意print和println的区别
public class Demo07 {
public static void main(String[] args) {
for (int i=0;i<=1000;i++){
if (i%5==0){
System.out.print(i);
System.out.print("\t");
}
if (i%15==0){
System.out.print("\n"); //System.out.println();也可
}
}
}
}
九九乘法表:
package Study;
public class Chengfabiao {
public static void main(String[] args) {
for (int i=1;i<=9;i++){
for (int j=1;j<=i;j++){
System.out.print(j+"*"+i+"="+i*j+" "); //注意这里是j*i
}
System.out.println();
}
}
}// \t是tab
break continue 以及 goto
输出三角形:
package Study;
public class Demo8 {
public static void main(String[] args) {
for (int i=1;i<=5;i++)
{
for (int j = 5; j >= i; j--) {
System.out.print(" ");
}
for (int j = 1; j <= i; j++) {
System.out.print("*");
}
for (int j = 1; j < i; j++) {
System.out.print("*");
}
System.out.println();
}
}
}