diff --git "a/02 \351\231\210\346\230\216\345\207\275/20221202 switch java.md" "b/02 \351\231\210\346\230\216\345\207\275/20221202 switch java.md"
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+#  第四次作业
+
+### 笔记
+
+
+
+```java
+switch (表达式) {
+case 1:
+语句体1;
+break;
+case 2:
+语句体2;
+break;
+...
+default: 
+语句体n+1;//(默认，不满足前面条件，则执行)
+break;//（可写可不写）
+    
+```
+
+### 作业1
+
+``` java
+public class D1 {
+    public static void main(String[] args) {
+        Scanner sc=new Scanner(System.in);
+        System.out.println("请输入星期几");
+        int x= sc.nextInt();
+        switch (x){
+            case 1:
+            case 2:
+            case 3:
+            case 4:
+            case 5:
+                System.out.println("工作日");
+                break;
+            case 6:
+            case 7:
+                System.out.println("休息日");
+                break;
+            default:
+                System.out.println("错误星期");
+                break;
+        }
+    }
+}
+```
+
+### 作业2
+
+``` java
+import java.util.Scanner;
+
+public class D2 {
+    public static void main(String[] args) {
+        Scanner sc =new Scanner(System.in);
+        System.out.println("请输入出租车");
+        String Taxi=sc.next();
+        System.out.println("请输入公里数");
+         double km= sc.nextDouble();
+        if (km<=3){
+            switch (Taxi){
+                case"夏利":{
+                    System.out.println("3元");
+                    break;}
+                case "富康":{
+                        System.out.println("4元");
+                        break;}
+                case"桑塔纳":{
+                    System.out.println("5元");
+                    break;
+                }
+            }
+        }
+        else if(km>3){
+            switch (Taxi){
+                case"夏利":{System.out.println((km-3)*2.1);
+                    break;}
+                case "富康":{System.out.println((km-3)*2.4);
+                break;}
+                case "桑塔纳":{System.out.println((km-3)*2.7);
+                break;}
+            }
+
+        }
+    }
+
+}
+
+```
+
+
+
+### 作业3
+
+``` java
+public class D3 {
+    public static void main(String[] args) {
+        Scanner sc = new Scanner(System.in);
+        System.out.println("今天是几月");
+        int yue = sc.nextInt();
+        System.out.println("今天是几日");
+        int day = sc.nextInt();
+        System.out.println("今年的年份");
+        int nian = sc.nextInt();
+        if (nian > 3000 && nian < 0) {
+            System.out.println("请重新输入");
+        } else if (nian % 4 == 0 && nian % 100 != 0 || nian % 400 == 0) {
+            switch (yue) {
+                case 1:
+                    System.out.println("今天是今年的" + (day + 1));
+                    break;
+                case 2:
+                    System.out.println("今天是今年的" + (31 + 1 + day));
+                    break;
+                case 3:
+                    System.out.println("今天是今年的" + (31 + 28 + 1 + day));
+                    break;
+                case 4:
+                    System.out.println("今天是今年的" + (31 + 28 + 31 + 1 + day));
+                    break;
+                case 5:
+                    System.out.println("今天是今年的" + (31 + 28 + 31 + 30 + 1 + day));
+                    break;
+                case 6:
+                    System.out.println("今天是今年的" + (31 + 28 + 31 + 30 + 31 + 1 + day));
+                    break;
+                case 7:
+                    System.out.println("今天是今年的" + (31 + 28 + 31 + 301 + 31 + 30 + day));
+                    break;
+                case 8:
+                    System.out.println("今天是今年的" + (31 + 28 + 31 + 30 + 31 + 30 + 31 + 1 + day));
+                    break;
+                case 9:
+                    System.out.println("今天是今年的" + (31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 1 + day));
+                    break;
+                case 10:
+                    System.out.println("今天是今年的" + (31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 1 + day));
+                    break;
+                case 11:
+                    System.out.println("今天是今年的" + (31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 1 + day));
+                    break;
+                case 12:
+                    System.out.println("今天是今年的" + (31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30 + 1 + day));
+                    break;
+                default:
+                    System.out.println("超出重新输入");
+                    break;
+            }
+        } else {
+            switch (yue){
+                case 1:
+                    System.out.println("今天是今年的" + (day));
+                    break;
+                case 2:
+                    System.out.println("今天是今年的" + (31 + day));
+                    break;
+                case 3:
+                    System.out.println("今天是今年的" + (31 + 28 + day));
+                    break;
+                case 4:
+                    System.out.println("今天是今年的" + (31 + 28 + 31 + day));
+                    break;
+                case 5:
+                    System.out.println("今天是今年的" + (31 + 28 + 31 + 30 + day));
+                    break;
+                case 6:
+                    System.out.println("今天是今年的" + (31 + 28 + 31 + 30 + 31 + day));
+                    break;
+                case 7:
+                    System.out.println("今天是今年的" + (31 + 28 + 31 + 30 + 31 + 30 + day));
+                    break;
+                case 8:
+                    System.out.println("今天是今年的" + (31 + 28 + 31 + 30 + 31 + 30 + 31 + day));
+                    break;
+                case 9:
+                    System.out.println("今天是今年的" + (31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + day));
+                    break;
+                case 10:
+                    System.out.println("今天是今年的" + (31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + day));
+                    break;
+                case 11:
+                    System.out.println("今天是今年的" + (31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + day));
+                    break;
+                case 12:
+                    System.out.println("今天是今年的" + (31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30 + day));
+                    break;
+                default:
+                    System.out.println("超出重新输入");
+                    break;
+            }
+        }
+    }
+}
+```
+