Day01
class 例子{
?? public static void main(String[] args){?
???? System.out.println("你好~~~");
?? }
}
Day02
public classDemo {
?? public static void main(String[] args){?
?? ?System.out.println("Hello");
???? System.out.println(3.02 - 2.89);
?? }
}
2、
public class OperatorDemo{
?? public static void main(String[] args){
???? /*
???? int i = 5;
???? int j = 7;
???? int k = i + j;
???? */
????
???? // int i = 5;
???? //表示先將i的值5取出來，然后+7，最后將結果再賦值給i
???? // i = i + 7;
???? /*
???? byte b1 = 5;
???? byte b2 = 7;
???? byte b = (byte)(b1 + b2);
???? */
???? /*
???? byte b = 5;
???? b = b + 7;
???? System.out.println(b);
???? */
???? // int i = 4200;
???? // double d = i / 1000 * 1000;
???? // double d = i / 1000.0 * 1000;
???? // System.out.println(d);
???? // System.out.println(5 / 0);
???? // System.out.println(5 / 0.0);
???? // System.out.println(-5.2 / 0);
???? System.out.println(0 / 0.0);????????????
?? }
}
3、
public classTypeDemo {
?? public static void main(String[] args){
???? System.out.println(10);
???? int i = 6;
???? int j = 7;
???? //當表示一個比較大的整數的時候，可以使用_進行分位，但是需要注意的是這種寫法是從JDK1.7出現的
???? int k = 5_482_637;
???? System.out.println(k);
???? long l1 = 15L;
???? System.out.println(l1);
???? float f1 = 5.87f;
???? float f2 = 2.854F;
????
???? char c = 'a';
???? //表示用utf-16編碼形式來寫這個字符
???? char c2 = '\ua4f3';
???? System.out.println(c);
???? System.out.println(c2);
???? System.out.println('\\');
????
???? boolean b = false;
???? System.out.println(b);
????
?? }
}
3
public classTypeDemo2 {
?? public static void main(String[] args){
???? /*
???? byte b = 125;
???? int i = b;
???? System.out.println(i);
???? */
????
???? // 1.23456794E9
???? // xey表示x*10^y
?? ?? /*
???? int i = 1234567890;
???? float d = i;
???? System.out.println(d);
???? */
????
???? /*
???? double d = 3e5;
???? System.out.println(d);
???? */
???? /*
???? float f = -25;
???? System.out.println(f);
???? */
????
???? /*
???? char c = 'a';
???? int i = c;
???? System.out.println(i);
???? */
????
???? /*
???? int i = 135;
???? byte b = (byte)i;
???? System.out.println(b);
???? */
????
???? /*
???? byte b = 127;
???? byte b2 = (byte)(b + 1);
???? System.out.println(b2);
???? */
????
???? double d = -6.9;
???? int i = (int)d;
???? System.out.println(i);
?? }
}
4、
public classVariableDemo {
?? public static void main(String[] args){
????
???? int i = 6;
???? System.out.println(i);
?? }?
}
DAY 03
1、
importjava.util.Scanner;
public classIfDemo {
?? public static void main(String[] args){
???? Scanner s = new Scanner(System.in);
???? int i = s.nextInt();
????
???? //判斷這個數字是否是3的倍數
???? if(i % 3 == 0)
??????? System.out.println(i + "是3的倍數");
?? }
}
2、
importjava.util.Scanner;
public classIfElseDemo {
?
?? public static void main(String[] args){
??
???? Scanner s = new Scanner(System.in);
???? int i = s.nextInt();
????
???? if(i % 2 == 1){
??????? System.out.println(i + "是一個奇數");
???? } else {
??????? System.out.println(i + "是一個偶數");
???? }
?? }
}
3、
importjava.util.Scanner;
public classIfElseExer {
??
?? public static void main(String[] args){
????
???? Scanner s = new Scanner(System.in);
???? int i = s.nextInt();
???? int j = s.nextInt();
???? int k = s.nextInt();
????
???? /*
???? if(i < j){
??????? if(i < k){
????????? System.out.println(i);
??????? } else {
????????? System.out.println(k);
??????? }
???? } else {
??????? if(j < k){
????????? System.out.println(j);
??????? } else {
????????? System.out.println(k);
??????? }
???? }
???? */
???? int min = i;
???? if(min > j)
??????? min = j;?
???? if(min > k)
??????? min = k;????
???? System.out.println(min);
?? }
??
}
4、
importjava.util.Scanner;
public classIfElseExer2 {
??
?? public static void main(String[] args){
????
???? Scanner s = new Scanner(System.in);
???? double weight = s.nextDouble();
????
???? double price = 0;
???? if(weight < 0){
??????? System.out.println("不合法的重量！！！");
???? } else {
??????? if(weight <= 20){
????????? price = weight * 0.35;
??????? } else {
????????? if(weight <= 100){
???????????? price = 20 * 0.35 + (weight - 20) *0.5;
????????? } else {
???????????? price = 20 * 0.35 + 80 * 0.5 +(weight - 100) * 0.8;
????????? }
??????? }
???????
???? }
????
???? System.out.println(price);
????
?? }
??
}
5、
importjava.util.Scanner;
public classIfElseIfDemo {
??
?? public static void main(String[] args){
????
???? Scanner s = new Scanner(System.in);
?? ?? doubleweight = s.nextDouble();
????
???? double price = 0;
????
???? if(weight < 0){
??????? System.out.println("非法的重量！！！");
???? } else if(weight <= 20){
??????? price = weight * 0.35;
???? } else if(weight <= 100){
??????? price = 7 + (weight - 20) * 0.5;
???? } else {
??????? price = 47 + (weight - 100) * 0.8;
???? }
????
???? System.out.println(price);
?? }
}
6、
importjava.util.Scanner;
public classIfElseIfExer {
??
?? public static void main(String[] args){
????
???? Scanner s = new Scanner(System.in);
???? int month = s.nextInt();
????
???? if(month < 1 || month > 12){
??????? System.out.println("Illegal month!!!");
???? } else if(month > 2 && month< 6){
??????? System.out.println("Spring");
???? } else if(month > 5 && month< 9){
??????? System.out.println("Summmer");
???? } else if(month > 8 && month< 12){
??????? System.out.println("Autumn");
???? } else {
??????? System.out.println("Winter");
???? }
????
????
?? }
??
}
?
7、
public classOperatorDemo {
??
?? public static void main(String[] args){
????
???? /*
???? int i = -9;
???? int j = 4;
???? System.out.println(i % j);
???? */
???? // System.out.println(5 % 1.4);
???? int i = 7;
???? //相當于在原來的基礎上來自加1
???? //先將i的值7取出來標記為結果，然后i自增為8，最后再將7賦值給j
???? // int j = i++;
???? //先將i自增為8，然后再將i的值賦值給j
???? // int j = ++i;
???? //先將i的值7取出來參與后續運算，然后i自增為8，用7參與乘法運算，結果就是14，最后將計算的14賦值給j
???? // int j = i++ * 2;
???? //先將i自增為8，然后將8取出來參與乘法運算，結果結果是16
???? int j = ++i * 2;
???? System.out.println(i);
???? System.out.println(j);
?? }
??
}
8、
public classOperatorDemo2 {
??
?? public static void main(String[] args){
????
???? /*
???? byte b = 127;
???? //在底層自動做了一次強制轉換
???? b++;
???? System.out.println(b);
???? */
????
???? /*
???? char c = '0';
???? System.out.println(c + 3);
???? */
????
???? // byte b = 130;
???? // 3和5是兩個字面量，字面量在參與運算的時候會自動的優化
???? //在編譯時期就會自動計算
???? // byte b = 8;
???? // byte b = 3 + 5;
???? // System.out.println(b);
????
???? // byte i = 5;
???? // i = i + 3;
???? // i += 33;
???? // i = i % 5;
???? // i %= 5;
???? // System.out.println(i);
????
???? // int i = j = k = 10;
???? // int i, j, k;
???? // i = j = k = 10;
????
???? /*
???? int i = 5;
???? i += i *= i -= 3;
???? System.out.println(i);
???? */
????
???? /*
???? System.out.println(3 == 5);
???? System.out.println(3 != 5);
???? int i = 5;
???? System.out.println(3 < i < 7);
???? */
????
???? /*
???? int i = 5, j = 7;
???? // boolean b = i++ >= 6 && j++> 3;
???? boolean b = j++ > 3 || i++ > 4;
???? System.out.println(i);
???? System.out.println(j);
???? System.out.println(b);
???? */
????
???? // int i = 3, j = 5, k = 6;
???? // boolean b = i++ > 0 || j++ > 5&& k++ < 10;
???? /*
???? boolean b = i++ > 5 && j++ >4 || k++ > 3;
???? System.out.println(i);
???? System.out.println(j);
???? System.out.println(k);
???? System.out.println(b);
???? */
????
???? int i = 5, j = 7, k = 4;
???? // int max = i > j ? i : j;
???? // System.out.println(max);
???? // i > j ? System.out.println(i) :System.out.println(j);
???? //三元表達式的嵌套
???? int max = i > j ? (i > k ? i : k) :(j > k ? j : k);
???? System.out.println(max);
?? }
}
?
9、
public classOperatorDemo3 {
?
?? public static void main(String[] args){
????
???? //如果算術>關系，先計算1+3=4，最后比較3>4，結果為false
???? //如果關系>算術，先計算3>1=true,然后true+1無法計算，會報錯
???? // System.out.println(3 > 1 + 3);
????
???? //如果關系>邏輯，先計算3>4=false,然后再計算true&false=false
???? //如果邏輯>關系，先計算true&3,無法計算，會報錯
???? // System.out.println(true & 3 > 4);
????
???? // System.out.println(1 & 6 + 3);
????
???? // System.out.println(2 << 3 > 3);
???? // System.out.println(2 & 3 > 2);
???? // System.out.println(2 << 3 + 3);
???? // System.out.println(~3 + 3);
???? // int i = 3, j = 5;
???? // System.out.println(i < j ? i : j +10);
???? // boolean b = i < j ? i : j > 4;
???? // System.out.println(i < j ? i : j ^5);
????
???? int i = 5;
???? // i = ~i++;
???? i = ~++i;
???? System.out.println(i);
?? }
}
10、
importjava.util.Scanner;
public classOperatorExer {
?? public static void main(String[] args){
???? Scanner s = new Scanner(System.in);
???? //從控制臺獲取一個小數
???? double score = s.nextDouble();
???? int i = s.nextInt();
????
???? char level = score >= 90 ? 'A' : (score>= 80 ? 'B' : (score >= 70 ? 'C' : (score >= 60 ? 'D' : 'E')));
???? System.out.println(level);
?? }
}
DAY 04
1、
importjava.util.Scanner;
public classWhileExer {
?
?? public static void main(String[] args){
????
???? // 1.求1-100以內所有的奇數的和
???? /*
???? //記錄和
???? int sum = 0;
???? int i = 1;
???? while(i <= 100){
??????? sum += i;
??????? i += 2;
???? }
???? System.out.println(sum);
???? */
????
???? // 2.打印100以內能被3整除而不能被7整除的數字
???? //思路：先獲取所有的3的倍數，然后再判斷這個倍數能否被7整除
???? /*
???? int i = 0;
???? while(i <= 100){
???????
??????? //判斷能否被7整除
??????? if(i % 7 != 0)
????????? System.out.println(i);
???????
??????? i += 3;
???? }
???? */
????
???? // 3.輸入一個數字，輸出這個數字是一個幾位數
?? ?? //思路：看能除以幾次10
???? /*
???? Scanner s = new Scanner(System.in);
???? int n = s.nextInt();
???? int count = 0;
???? while(n != 0){
??????? n /= 10;
??????? count++;
???? }
???? System.out.println(count);
???? */
????
???? // 4.輸入一個數字，輸出這個數字的所有的因數
???? Scanner s = new Scanner(System.in);
???? int n = s.nextInt();
???? int i = 1;
???? while(i <= n){
???????
??????? if(n % i == 0)
????????? System.out.println(i);
???????
??????? i++;
???? }
????
?? }
?
}
2
public classWhileDemo {
?
?? public static void main(String[] args){
????
???? /*
???? //表示次數
???? int count = 0;
???? while(count < 10){
??????? System.out.println("Hello");
??????? count++;
???? }
???? */
????
???? /*
???? //打印1-10
???? int i = 1;
???? while(i <= 10){
??????? System.out.println(i);
??????? i++;
???? }
???? */
????
???? //求1-100的和
???? int sum = 0;
???? int i = 1;
???? // while循環的條件是必須寫的
???? while(){
??????? sum += i;
??????? i++;
???? }
???? System.out.println(sum);
????
????
?? }
?
}
3
importjava.util.Scanner;
public classSwitchCaseExer2 {
??
?? public static void main(String[] args){
????
???? //獲取年月日
???? Scanner s = new Scanner(System.in);
???? int year = s.nextInt();
???? int month = s.nextInt();
???? int day = s.nextInt();
????
???? //定義一個變量來記錄總天數
???? int sum = 0;
????
???? //根據月份確定到底要加上多少天
???? switch(month){
??????? case 12:sum += 30; //經歷11月的30天
??????? case 11:sum += 31; //經歷10月的31天
??????? case 10:sum += 30;
??????? case 9: sum += 31;
??????? case 8: sum += 31;
??????? case 7: sum += 30;
??????? case 6: sum += 31;
??????? case 5: sum += 30;
??????? case 4: sum += 31;
??????? case 3: //加上2月的天數 - 平年和閏年的判斷
????????? if(year % 100 != 0 && year % 4== 0 || year % 400 == 0){
???????????? sum += 29;
????????? } else {
???????????? sum += 28;
????????? }
??????? case 2: sum += 31;
??????? case 1: sum += day;
???? }
???? System.out.println(sum);
????
?? }
??
}
4、
importjava.util.Scanner;
public classSwitchCaseExer {
??
?? public static void main(String[] args){
????
???? //獲取兩個數字和一個符號
???? Scanner s = new Scanner(System.in);
???? double m = s.nextDouble();
???? double n = s.nextDouble();
???? String symbol = s.next();
????
???? //根據符號確定要進行的運算
???? switch(symbol){
??????? case "+":
????????? System.out.println(m + n);
????????? break; //表示結束當前的選項
??????? case "-":
????????? System.out.println(m - n);
????????? break;
??????? case "*":
????????? System.out.println(m * n);
????????? break;
??????? case "/":
????????? System.out.println(m / n);
????????? break;
??????? case "%":
????????? System.out.println(m % n);
????????? break;
??????? default:
????????? System.out.println("符號非法！！！");
????????? break;
???? }
????
?? }
??
}
5
importjava.util.Scanner;
public classSwitchCaseDemo2 {
?
?? public static void main(String[] args){
????
???? Scanner s = new Scanner(System.in);
???? // int i = s.nextInt();
????
???? /*
???? int j = 0;
???? switch(i){
???????
??????? //如果沒有break，那么代碼從匹配的case開始，順次往下執行，直到遇到break；
??????? case 0 : j += 3;
??????? case 2 : j += 6;break;
??????? case 1 : j += 4;break;
??????? case 3 : j += 7;break;
???????
???? }
????
???? System.out.println(j);
???? */
????
???? //輸入數字表示月份，然后輸出這個月份對應的天數（平年）
???? // 31天：1 3 5 7 8 10 12
???? // 30天：4 6 9 11
???? // 28天：2
???? int month = s.nextInt();
???? switch(month){
??????? case 1:
??????? case 3:
??????? case 5:
??????? case 7:
??????? case 8:
??????? case 10:
??????? case 12:
????????? System.out.println(31);break;
??????? case 4:
??????? case 6:
??????? case 9:
??????? case 11:
????????? System.out.println(30);
????????? break;
??????? case 2:
????????? System.out.println(28);
????????? break;
??????? default:
????????? System.out.println("Illegalmonth!!!");break;
???? }
?? }
?
}
6、
importjava.util.Scanner;
public classSwitchCaseDemo {
??
?? public static void main(String[] args){
????
???? Scanner s = new Scanner(System.in);
???? int n = s.nextInt();
????
???? switch(n){
??????? case 4:
????????? System.out.println("星期四");break;
??????? case 2:
????????? System.out.println("星期二");break;
??????? case 5:
????????? System.out.println("星期五");break;
??????? case 3:
????????? System.out.println("星期三");break;
??????? case 6:
????????? System.out.println("星期六");break;
??????? case 1:
????????? System.out.println("星期一");break;
??????? case 7:
????????? System.out.println("星期天");break;
??????? //只要其他的case都不符合則自動劃歸到default
??????? default:
????????? System.out.println("星期不合法！！！");break;
???? }?
?? }
}
7、
public classLoopExer {
?
?? 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) + "\t");
??????? }
??????? System.out.println();
???????
???? }
???? */
????
???? /*
????????? *****
??????? ??*****
??????? ?*****
??????? ?*****
??????? *****
???? */
???? /*
???? for(int i = 1; i <= 5; i++){
???????
??????? for(int j = 1; j <= 5 - i; j++)
????????? System.out.print("");
???????
??????? for(int j = 1; j <= 5; j++)
????????? System.out.print("*");
???????
??????? System.out.println();
???? }
???? */
????
???? //百錢百雞
???? for(int i = 1; i < 33; i++){ //表示公雞的個數
??????? for(int j = 1; j < 50; j++){//表示母雞的個數
????????? //計算小雞的個數
????????? int k = 100 - i - j;
????????? if(k % 3 == 0 && i * 3 + j * 2+ k / 3 == 100){
???????????? System.out.println("公雞" + i);
???????????? System.out.println("母雞" + j);
???????????? System.out.println("小雞" + k);
???????????? System.out.println("==================");
????????? }
??????? }?
???? }???
?? }
}
8、
importjava.util.Scanner;
public class LoopDemo2{
??
?? public static void main(String[] args){
????
???? Scanner s = new Scanner(System.in);
???? int n = s.nextInt();
????
???? //標記這個數字是否是一個質數
???? //規定如果為true表示是一個質數，如果為false表示不是一個質數
???? boolean b = true;
????
???? //判斷一個數字是否是一個質數
???? //從2開始逐個往后取余，看是否還有別的因數，如果沒有別的因數，那么就是一個質數，反之就說明不是質數
???? for(int i = 2; i < n; i++){
??????? //如果能夠取余，說明n除了1和本身以外還有別的因數，那么n就不是質數
??????? if(n % i == 0){
????????? b = false;
????????? break;
??????? }
???????
???? }
????
???? if(b)
??????? System.out.println(n + "是一個質數");
???? else
??????? System.out.println(n + "不是一個質數");
????
?? }
??
}
9、
public classLoopDemo {
?
?? public static void main(String[] args){
???? // *******
???? /*
???? for(int i = 1; i <= 7; i++){
??????? //不換行打印
??????? // ln -> line
??????? System.out.print("*");
???? }
???? System.out.println();
???? */
?
???? /*
??????? *******
??????? *******
??????? *******
??????? *******
???? */
???? //循環的嵌套
???? /*
???? for(int count = 1; count <= 5; count++){
??????? for(int i = 1; i <= 7; i++){
????????? System.out.print("*");
??????? }
??????? System.out.println();
???? }
???? */
?
???? /*
??????? *
??????? **
??????? ***
??????? ****
??????? *****
??????? ******
??????? 行數：1 -> n
??????? 第i行*的個數：1->i
???? */
???? /*
???? for(int i = 1; i <= 6; i++){
??????? for(int j = 1; j <= i; j++){
????????? System.out.print("*");
??????? }
??????? System.out.println();
???? }
???? */
???? /*
??????? ******
??????? *****
??????? ****
??????? ***
??????? **
??????? *
??????? 行數：n -> 1
??????? 每一行的*的個數：i -> 1
???? */
???? /*
???? for(int i = 6; i > 0; i--){
??????? for(int j = i; j > 0; j--){
????????? System.out.print("*");
??????? }
??????? System.out.println();
???? }
???? */
????
???? /*
??????? -----*
??????? ----**
??????? ---***
??????? --****
??????? -*****
??????? ******
??????? 行數：1 -> n
??????? 空格的個數：1 -> n-i
??????? *的個數：1 -> i
???? */
???? /*
???? for(int i = 1; i <= 6; i++){
??????? //先打印空格
??????? for(int j = 1; j <= 6 - i; j++){
????????? System.out.print("");
??????? }
??????? //打印*
??????? for(int k = 1; k <= i; k++){
????????? System.out.print("*");
??????? }
??????? System.out.println();
???? }
???? */
????
???? /*
??????? ******
??????? ?*****
??????? ?****
??????? ??***
??????? ???**
????????? ?*
??????? 行數：n -> 1
??????? 空格個數：n-i -> 1
??????? *的個數：i -> 1
???? */
???? for(int i = 6; i > 0; i--){
???????
??????? for(int j = 6 - i; j > 0; j--)
????????? System.out.print("");
???????
??????? for(int j = i; j > 0; j--)
????????? System.out.print("*");
???????
??????? System.out.println();
???????
10、
importjava.util.Scanner;
public classIfElseIfExer {
??
?? public static void main(String[] args){
????
???? //輸入數字
???? Scanner s = new Scanner(System.in);
???? int n = s.nextInt();
????
???? //判斷這個數字是否合法
???? if(n < 1 || n > 7){
??????? System.out.println("星期不合法！！！");
???? } else if(n == 1){
??????? System.out.println("星期一");
???? } else if(n == 2){
??????? System.out.println("星期二");
???? } else if(n == 3){
??????? System.out.println("星期三");
???? } else if(n == 4){
??????? System.out.println("星期四");
???? } else if(n == 5){
??????? System.out.println("星期五");
???? } else if(n == 6){
??????? System.out.println("星期六");
???? } else {
??????? System.out.println("星期天");
11、
public classForDemo {
?
?? public static void main(String[] args){
????
???? /*
???? for(int i = 1; i <= 10; i++){
??????? System.out.println("Hello");
???? }
???? */
????
???? //求1-50的和
???? int sum = 0;
???? // for()內有3部分組成
???? //對于for循環而言，如果第二部分的控制條件沒有寫，那么默認為true，這個時候就成了一個死循環
???? for(int i = 1; i <= 10; i++){
??????? sum += i;
???? }
???? // System.out.println(sum);
????
12、
public classForDemo {
?
?? public static void main(String[] args){
????
???? /*
???? for(int i = 1; i <= 10; i++){
??????? System.out.println("Hello");
???? }
???? */
????
???? //求1-50的和
???? int sum = 0;
???? // for()內有3部分組成
???? //對于for循環而言，如果第二部分的控制條件沒有寫，那么默認為true，這個時候就成了一個死循環
???? for(int i = 1; i <= 10; i++){
??????? sum += i;
???? }
???? // System.out.println(sum);
??
13、
public classContinueDemo {
?
?? public static void main(String[] args){
??
???? /*
???? for(int i = 1; i < 5; i++){
???????
??????? if(i % 2 == 0)
????????? //表示這次循環直接跳過，執行下一次的循環
????????? continue;
???????
??????? System.out.println(i);
???????
???? }
???? */
???? for(int i = 1; i < 5; i++){
???????
??????? for(int j = 1; j < 5; j++){
?????????
????????? if(j % 2 == 0)
???????????? continue;
?????????
????????? System.out.println(i + "," +j);
?????????
14、
public classBreakDemo {
?
?? public static void main(String[] args){
????
???? /*
???? for(int i = 1; i < 5; i++){
???????
??????? if(i % 2 == 0)
????????? //表示遇到了break之后，循環結構就會結束
????????? break;
???????
??????? System.out.println(i);
???????
???? }
???? */
????
???? for(int i = 1; i < 5; i++){
???????
??????? for(int j = 1; j < 5; j++){
?????????
????????? if(j % 3 == 0)
???????????? //表示終止當前的一層結構
???????????? break;
?????????
????????? System.out.println(i + "," +j);
?????????
15、
public class ArrayDemo{
?? public static void main(String[] args){
????
???? byte[] arr = new byte[5];
???? // arr[2] = 10;
???? //最大下標為4
???? // ArrayIndexOutOfBoundsException -數組下標越界異常
???? // arr[5] = 7;
???? // System.out.println(arr[2]);
???? // boolean[] bs = new boolean[4];
???? // String[] arr = new String[7];
???? System.out.println(arr);
???? // System.out.println(arr[1]);
????
16、
?
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