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Javs运算符及选择语句结构
运算符:
逻辑运算符:&&、||为二目运算符,!为单目运算符
注意:(逻辑运算符的操作数必须是布尔型数据)
例如:2>8&&9>2 的结果为为 false;
自增运算符:
a++ = a = a + 1;
ASCII码:0十进制为48,A十进制为65,a十进制为97。
二进制满1上,十进制满9上,十六制满15上。
If else 语句
int month = 12;
if (month == 2) {
System.out.println(month + "月有28天");
} else if (month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10 || month == 12) {
System.out.println(month + "月有31天");
}
else if(month == 4 || month == 6|| month == 9 || month == 11)
{
System.out.println(month + "月有30天");
}
else {
System.out.println("请输入一个正确的月份");
}
switch 语句
public class SweiChi
{
public static void main(String[] args)
{
System.out.println("请输入一个月份:");
Scanner scanner = new Scanner(System.in);
int aaa=scanner.nextInt();
switch (aaa){
case 2:
System.out.println(aaa+"月份有28天,29天");
break;
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
System.out.println(aaa+"月份有31天");
break;
case 4:
case 6:
case 9:
case 11:
System.out.println(aaa+"月份有30天");
break;
default:
System.out.println("请输入1-12月份");
break;
}
}
}
do while 语句
while (1>0) {
int i = 1, sum = 0, n = 0;
Scanner scanner = new Scanner(System.in);
String a = scanner.next();
n = Integer.parseInt(a);
do {
sum += i;
i++;
}
while (i <= n);
System.out.println(“1+2+…+” + n + “=” + sum);
for循环语句
for(赋初值;判断条件;赋值增减量)