Java中常用的赋值运算符
+= 将该运算符左边的数值加上右边的数值, 其结果赋值给左边变量本身
-= 将该运算符左边的数值减去右边的数值, 其结果赋值给左边变量本身
*= 将该运算符左边的数值乘以右边的数值, 其结果赋值给左边变量本身
/= 将该运算符左边的数值整除右边的数值, 其结果赋值给左边变量本身
%= 将该运算符左边的数值除以右边的数值后取余,其结果赋值给左边变量本身
Java注释:
分为单行注释,多行注释(块注释),文档注释
注释可以提高代码可读性,方便后期代码维护,
方便程序员间的交流沟通生成帮助文档。
同时注释不能长篇大论,也不能过于简单。
switch语句
switch中的值只能是整数、枚举、字符、字符串
不可使用long、float、double、boolean作为它的数据类型
交换三个值(代码):
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
int a = scan.nextInt();
int b = scan.nextInt();
int tmp = a;
a = b;
b = tmp;
System.out.println("a = " + a);
System.out.println("b = " + b);
}
}
求三个数中的最值(代码):
public static void main(String[] args) {
int a = 4;
int b = 2;
int c = 3;
int max = 0;
int min = 0;
if (a > b && a > c){
max = a;
}
else if (b > a && b > c){
max = b;
}
else
max = c;
if (a < b && a < c) {
min = a;
}
else if (b < a && b < c) {
min = b;
}
else
min = c;
System.out.println("max = " + max);
System.out.println("min = " + min);
}
public static void main(String[] args) {
int count = 0;
for (int i = 1; i < 100; i++) {
if(i % 10 == 9) {
count++;
}else if(i / 10 == 9) {
count++;
}
}
System.out.println(count);
}
public static void main(String[] args) {
for(int year = 1000;year <= 2000;year++){
if((year % 4 == 0 && year % 100 != 0) || year % 400 ==0){
System.out.println(year);
}
}
}
public static void main(String[] args) {
int count = 0;
for (int i = 2; i < 101; i++) {
for (int j = 2; j <= i; j++) {
if (i % j == 0 && i != j)
break;
if (j == i) {
if (count % 5 == 0)
System.out.println();
System.out.print(j + " ");
count++;
}
}
}
System.out.println("\n素数有" + count + "个");
}
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int num = scanner.nextInt();
for (int j = 0; j <= num; j++) {
int i = 2;
for (; i <= Math.sqrt(j); i++) {
if (num % i == 0) {
System.out.println("不是素数");
break;
}
}
if (i > Math.sqrt(num)) {
System.out.println("是素数");
break;
}
}
}
public static void main(String[] args) {
while(true){
System.out.println("请输入要判断的年龄");
Scanner in=new Scanner(System.in);
int age=in.nextInt();
if(age<0){
System.out.println("输入有误,重新输入");
continue;
}
if(age>=0&&age<=18){
System.out.println("少年");
break;
}
if(age>=19&&age<=28){
System.out.println("少年");
break;
}
if(age>=29&&age<=55){
System.out.println("中年");
break;
}
else{
System.out.println("老年");
break;
}
}
}
public static void printX(int m) {
for (int x = 1; x <= m; x++) {
for (int y = 1; y <= m; y++) {
if (x == y || x + y == m + 1) {
System.out.print("*");
} else {
System.out.print(" ");
}
}
System.out.println();
}
}
public static void main(String[] args) {
printX(10);
}
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
Random random = new Random();
int ranNum = random.nextInt(100) + 1;
while (true){
int num = scanner.nextInt();
if (num < ranNum) {
System.out.println("小");
}else if (num > ranNum) {
System.out.println("大");
}else{
System.out.println("==");
break;
}
}
}
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int n = scanner.nextInt();
for (int i = 1; i <= n ; i++) {
int count = 0;
int tmp = i ;
while (tmp != 0) {
count++;
tmp = tmp/10;
}
tmp = i;
int sum = 0;
while (tmp != 0) {
sum += Math.pow(tmp%10,count);
tmp = tmp/10;
}
if(sum == i) {
System.out.println(i);
}
}
public class Main {
public static double func(int i,int j) {
double ret = 1.0/i - 1.0/j;
return ret;
}
public static void main(String[] args) {
double sum = 0.0;
for (int i = 1; i < 100 ; i+=2) {
sum = sum+ func(i,i+1);
}
System.out.println(sum);
}
public static void main(String[] args) {
int a = 9;
int b = 18;
int c = 0;
while (a % b != 0) {
c = a %b;
a = b;
b = c;
}
System.out.println(c);
}
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int num = scanner.nextInt();
int count = 0;
for(int i = 0;i < 32;i++) {
if(((num >> i) & 1) == 1) {
count++;
}
}
System.out.println(count);
}
}
public static void main(String[] args) {
int num = 14;
odd(num);
System.out.println();
even(num);
}
public static void odd(int num) {
for (int i = 30; i >= 0; i = i - 2) {
if ((num & (1 << i)) != 0) {
System.out.print("1 ");
} else {
System.out.print("0 ");
}
}
}
public static void even(int num) {
for (int i = 31; i >= 0; i = i - 2) {
if ((num & (1 << i)) != 0) {
System.out.print("1 ");
} else {
System.out.print("0 ");
}
}
}
public static void main(String[] args) {
int count = 3;
Scanner scanner = new Scanner(System.in);
while (count != 0) {
String passWorld = scanner.nextLine();
if(passWorld.equals("123456")) {
System.out.println("登录成功!");
}else {
count--;
}
}
}
public static void print (int n) {
if(n < 0) {
//变成整数。
System.out.println("-");
n = -n;
}
if(n>9) {
print(n/10);//递归
}
System.out.println(n%10);//打印个位数
}
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
int n = scan.nextInt();
print(n);
}
public static void main(String[] args) {
for (int i = 1; i <= 9; i++) {
for (int j = 1; j <= i ; j++) {
System.out.print(i+"*"+j + "=" + i*j +" ");
}
System.out.println();
}
}
over!
我像个憨批研究了半天为什么我的表情包下面有水印…绝了(过了考试周智商就没有了)