程序逻辑控制(2)
一.循环结构
1.while循环
while(循环条件){
循环语句;
}
- 打印1-10的数字;
- 计算1-100的和;
- 计算5的阶乘;
- 计算 1! + 2! + 3! + 4! + 5!的结果;
public static void main(String[] args) {
int num = 1;
while(num <= 10){
System.out.println(num);
num++;
}
int n = 1;
int result = 0;
while(n <=100 ){
result += n;
n++;
}
System.out.println("1-100的和为: "+result);
int m = 1;
int res = 1;
while(m <= 5){
res *= m;
m++;
}
System.out.println("5的阶乘是: "+res);
int nums = 1;
int sum = 0;
while(nums <= 5){
int fac = 1;
int tmp = 1;
while(tmp <= nums){
fac *= tmp;
tmp++;
}
sum += fac;
nums++;
}
System.out.println("1! + 2! + 3! + 4! + 5!的结果是: "+sum);
2.for循环
- 表达式1: 用于初始化循环变量.
- 表达式2: 循环条件
- 表达式3: 更新循环变量
for(表达式1;表达式2;表达式3){
循环体;
}
public static void main(String[] args) {
int sum = 0;
for (int i = 1; i <= 100; i++) {
sum += i;
}
System.out.println("sum = " + sum);
int result = 1;
for (int i = 1; i <= 5; i++) {
result *= i;
}
System.out.println("result = " + result);
int sums = 0;
for (int i = 1; i <= 5; i++) {
int tmp = 1;
for (int j = 1; j <= i; j++) {
tmp *= j;
}
sums += tmp;
}
System.out.println("sums = " + sums);
}
3.break和continue
public static void main(String[] args) {
int num = 100;
while (num <= 200) {
if (num % 3 == 0) {
System.out.println("找到了 3 的倍数, 为:" + num);
break;
}
num++;
}
}
找到了 3 的倍数, 为:102(因为102已经找到了,所以直接就跳出循环,不在循环了)
public static void main(String[] args) {
int num = 100;
while (num <= 200) {
if (num % 3 != 0) {
num++;
continue;
}
System.out.println("找到了 3 的倍数, 为:" + num);
num++;
}
}