update:demo6

.gitignore

@@ -0,0 +1,95 @@
+### Compiled class files
+*.class
+
+### Log files
+*.log
+
+### BlueJ files
+*.ctxt
+
+### Mobile Tools for Java (J2ME)
+.mtj.tmp/
+
+### Package Files
+*.jar
+*.war
+*.nar
+*.ear
+*.zip
+*.tar.gz
+*.rar
+
+### VM crash logs
+hs_err_pid*
+replay_pid*
+
+# ========================
+# Maven
+# ========================
+target/
+pom.xml.tag
+pom.xml.releaseBackup
+pom.xml.versionsBackup
+pom.xml.next
+release.properties
+dependency-reduced-pom.xml
+buildNumber.properties
+.mvn/timing.properties
+.mvn/wrapper/maven-wrapper.jar
+
+# ========================
+# Gradle
+# ========================
+.gradle/
+build/
+!gradle-wrapper.jar
+!*/src/main/**/build/
+!*/src/test/**/build/
+
+### Avoid ignoring Gradle wrapper
+gradle-app.setting
+
+# ========================
+# IntelliJ IDEA
+# ========================
+.idea/
+*.iml
+*.ipr
+*.iws
+out/
+
+# ========================
+# Eclipse
+# ========================
+.project
+.classpath
+.cproject
+.settings/
+bin/
+tmp/
+
+# ========================
+# NetBeans
+# ========================
+nbproject/private/
+nbbuild/
+dist/
+nbdist/
+.nb-gradle/
+
+# ========================
+# VS Code
+# ========================
+.vscode/
+
+# ========================
+# OS files
+# ========================
+# macOS
+.DS_Store
+
+# Windows
+Thumbs.db
+
+#local
+com/study/test/

com/study/demo/Demo.java

@@ -1,7 +1,7 @@
 package com.study.demo;
 
 public class Demo {
-	public static void main(String [] args) {
-		System.out.println("HelloWorld!");
-		}
+  public static void main(String[] args) {
+    System.out.println("HelloWorld!");
+  }
 }

com/study/demo/test1_1.java

@@ -1,13 +1,15 @@
 package com.study.demo;
+
 import java.util.Scanner;
+
 // I am 212306206
 public class test1_type {
-	public static void main(String[] args) {
-		Scanner scanner = new Scanner (System.in);
-		int a = scanner.nextInt();
-		int b = scanner.nextInt();
-		int sum = a + b;
-		System.out.println(a + " + " + b + " = " + sum);
-		scanner.close();
-	}
+  public static void main(String[] args) {
+    Scanner scanner = new Scanner(System.in);
+    int a = scanner.nextInt();
+    int b = scanner.nextInt();
+    int sum = a + b;
+    System.out.println(a + " + " + b + " = " + sum);
+    scanner.close();
+  }
 }

com/study/demo/test1_2.java

@@ -1,16 +1,15 @@
 package com.study.demo;
 
 public class test2_for {
-    public static void main(String[] args) {
-        int[] numbers = new int[5];
-        for (int i = 0; i < numbers.length; i++) {
-            numbers[i] = i * 10;
-        }
-
-        System.out.print("数组内容: ");
-        for (int i = 0; i < numbers.length; i++) {
-            System.out.print(numbers[i] + " ");
-        }
+  public static void main(String[] args) {
+    int[] numbers = new int[5];
+    for (int i = 0; i < numbers.length; i++) {
+      numbers[i] = i * 10;
     }
-}
 
+    System.out.print("数组内容: ");
+    for (int i = 0; i < numbers.length; i++) {
+      System.out.print(numbers[i] + " ");
+    }
+  }
+}

com/study/demo/test1_3.java

@@ -1,19 +1,18 @@
 package com.study.demo;
 
 public class test3_1_99 {
-    public static void main(String[] args) {
-        int[] numbers = new int[99];
+  public static void main(String[] args) {
+    int[] numbers = new int[99];
 
-        for (int i = 0; i < numbers.length; i++) {
-            numbers[i] = i + 1;
-        }
-
-        int sum = 0;
-        for (int i = 0; i < numbers.length; i++) {
-            sum += numbers[i];
-        }
-
-        System.out.println("1+2+...+99 的和 = " + sum);
+    for (int i = 0; i < numbers.length; i++) {
+      numbers[i] = i + 1;
     }
-}
 
+    int sum = 0;
+    for (int i = 0; i < numbers.length; i++) {
+      sum += numbers[i];
+    }
+
+    System.out.println("1+2+...+99 的和 = " + sum);
+  }
+}

com/study/demo/test2_2.java

@@ -1,14 +1,15 @@
 package com.study.demo;
+
 import java.util.Scanner;
 
 public class test5 {
-    public static void main(String[] args) {
-        Scanner scanner = new Scanner(System.in);
-        int a = scanner.nextInt();
-        int b = scanner.nextInt();
-        int c = scanner.nextInt();
-        double pi = 3.1415926535;
-        double area = a * b * c + a * c + (pi * c * c) / 4;
-        System.out.printf("%.3f\n", area / 10000);
-    }
-}
+  public static void main(String[] args) {
+    Scanner scanner = new Scanner(System.in);
+    int a = scanner.nextInt();
+    int b = scanner.nextInt();
+    int c = scanner.nextInt();
+    double pi = 3.1415926535;
+    double area = a * b * c + a * c + (pi * c * c) / 4;
+    System.out.printf("%.3f\n", area / 10000);
+  }
+}

com/study/demo/test2_3.java

@@ -3,10 +3,10 @@ package com.study.demo;
 import java.util.Scanner;
 
 public class test6 {
-    public static void main(String[] args) {
-        Scanner scanner = new Scanner(System.in);
-        int n = scanner.nextInt();
-        int result = 1 << n;
-        System.out.println(result);
-    }
-}
+  public static void main(String[] args) {
+    Scanner scanner = new Scanner(System.in);
+    int n = scanner.nextInt();
+    int result = 1 << n;
+    System.out.println(result);
+  }
+}

com/study/demo/test2_4.java

@@ -3,12 +3,12 @@ package com.study.demo;
 import java.util.Scanner;
 
 public class test7 {
-    public static void main(String[] args) {
-        Scanner scanner = new Scanner(System.in);
-        int x = scanner.nextInt();
-        int y = scanner.nextInt();
-        int startYear = 2016, startMonth = 8;
-        int totalMonths = (x - startYear) * 12 + y - startMonth + 1;
-        System.out.println(totalMonths);
-    }
-}
+  public static void main(String[] args) {
+    Scanner scanner = new Scanner(System.in);
+    int x = scanner.nextInt();
+    int y = scanner.nextInt();
+    int startYear = 2016, startMonth = 8;
+    int totalMonths = (x - startYear) * 12 + y - startMonth + 1;
+    System.out.println(totalMonths);
+  }
+}

com/study/demo/test2_5.java

@@ -3,17 +3,17 @@ package com.study.demo;
 import java.util.Scanner;
 
 public class test8 {
-    public static void main(String[] args) {
-        Scanner scanner = new Scanner(System.in);
-        int x = scanner.nextInt();
-        int k = scanner.nextInt();
-        int a = x / 1000 % k;
-        int b = x / 100 % 10 % k;
-        int c = x / 10 % 10 % k;
-        int d = x % 10 % k;
-        System.out.print(a);
-        System.out.print(b);
-        System.out.print(c);
-        System.out.println(d);
-    }
+  public static void main(String[] args) {
+    Scanner scanner = new Scanner(System.in);
+    int x = scanner.nextInt();
+    int k = scanner.nextInt();
+    int a = x / 1000 % k;
+    int b = x / 100 % 10 % k;
+    int c = x / 10 % 10 % k;
+    int d = x % 10 % k;
+    System.out.print(a);
+    System.out.print(b);
+    System.out.print(c);
+    System.out.println(d);
+  }
 }

com/study/demo/test3_1.java

@@ -3,20 +3,20 @@ package com.study.demo;
 import java.util.Scanner;
 
 public class test3_1 {
-    public static void main(String[] args) {
-        Scanner scanner = new Scanner(System.in);
-        int n = scanner.nextInt();
-        int[] arr = new int[n];
-        for (int i = 0; i < n; i++) {
-            arr[i] = scanner.nextInt();
-        }
-        for (int i = 0; i < n / 2; i++) {
-            int temp = arr[i];
-            arr[i] = arr[n - 1 - i];
-            arr[n - 1 - i] = temp;
-        }
-        for (int i = 0; i < n; i++) {
-            System.out.print(arr[i] + (i == n - 1 ? "" : " "));
-        }
+  public static void main(String[] args) {
+    Scanner scanner = new Scanner(System.in);
+    int n = scanner.nextInt();
+    int[] arr = new int[n];
+    for (int i = 0; i < n; i++) {
+      arr[i] = scanner.nextInt();
     }
+    for (int i = 0; i < n / 2; i++) {
+      int temp = arr[i];
+      arr[i] = arr[n - 1 - i];
+      arr[n - 1 - i] = temp;
+    }
+    for (int i = 0; i < n; i++) {
+      System.out.print(arr[i] + (i == n - 1 ? "" : " "));
+    }
+  }
 }

com/study/demo/test3_2.java

@@ -3,21 +3,21 @@ package com.study.demo;
 import java.util.Scanner;
 
 public class test3_2 {
-    public static void main(String[] args) {
-        Scanner scanner = new Scanner(System.in);
-        int n = scanner.nextInt();
-        int[] a = new int[n];
-        int[] b = new int[n];
-        for (int i = 0; i < n; i++) {
-            a[i] = scanner.nextInt();
-        }
-        for (int i = 0; i < n; i++) {
-            b[i] = scanner.nextInt();
-        }
-        int sum = 0;
-        for (int i = 0; i < n; i++) {
-            sum += a[i] * b[i];
-        }
-        System.out.println(sum);
+  public static void main(String[] args) {
+    Scanner scanner = new Scanner(System.in);
+    int n = scanner.nextInt();
+    int[] a = new int[n];
+    int[] b = new int[n];
+    for (int i = 0; i < n; i++) {
+      a[i] = scanner.nextInt();
     }
+    for (int i = 0; i < n; i++) {
+      b[i] = scanner.nextInt();
+    }
+    int sum = 0;
+    for (int i = 0; i < n; i++) {
+      sum += a[i] * b[i];
+    }
+    System.out.println(sum);
+  }
 }

com/study/demo/test3_3.java

@@ -3,23 +3,23 @@ package com.study.demo;
 import java.util.Scanner;
 
 public class test3_3 {
-    public static void main(String[] args) {
-        Scanner scanner = new Scanner(System.in);
-        int n = scanner.nextInt();
-        int[] arr = new int[n];
-        for (int i = 0; i < n; i++) {
-            arr[i] = scanner.nextInt();
-        }
-        int maxLen = 1, currentLen = 1;
-        for (int i = 1; i < n; i++) {
-            if (arr[i] == arr[i - 1]) {
-                currentLen++;
-            } else {
-                maxLen = Math.max(maxLen, currentLen);
-                currentLen = 1;
-            }
-        }
-        maxLen = Math.max(maxLen, currentLen);
-        System.out.println(maxLen);
+  public static void main(String[] args) {
+    Scanner scanner = new Scanner(System.in);
+    int n = scanner.nextInt();
+    int[] arr = new int[n];
+    for (int i = 0; i < n; i++) {
+      arr[i] = scanner.nextInt();
     }
+    int maxLen = 1, currentLen = 1;
+    for (int i = 1; i < n; i++) {
+      if (arr[i] == arr[i - 1]) {
+        currentLen++;
+      } else {
+        maxLen = Math.max(maxLen, currentLen);
+        currentLen = 1;
+      }
+    }
+    maxLen = Math.max(maxLen, currentLen);
+    System.out.println(maxLen);
+  }
 }

com/study/demo/test3_4.java

@@ -3,21 +3,21 @@ package com.study.demo;
 import java.util.Scanner;
 
 public class test3_4 {
-    public static void main(String[] args) {
-        Scanner scanner = new Scanner(System.in);
-        int n = scanner.nextInt();
-        int m = scanner.nextInt();
-        int[][] image = new int[n][m];
-        for (int i = 0; i < n; i++) {
-            for (int j = 0; j < m; j++) {
-                image[i][j] = scanner.nextInt();
-            }
-        }
-        for (int j = 0; j < m; j++) {
-            for (int i = n - 1; i >= 0; i--) {
-                System.out.print(image[i][j] + (i == 0 ? "" : " "));
-            }
-            System.out.println();
-        }
+  public static void main(String[] args) {
+    Scanner scanner = new Scanner(System.in);
+    int n = scanner.nextInt();
+    int m = scanner.nextInt();
+    int[][] image = new int[n][m];
+    for (int i = 0; i < n; i++) {
+      for (int j = 0; j < m; j++) {
+        image[i][j] = scanner.nextInt();
+      }
     }
+    for (int j = 0; j < m; j++) {
+      for (int i = n - 1; i >= 0; i--) {
+        System.out.print(image[i][j] + (i == 0 ? "" : " "));
+      }
+      System.out.println();
+    }
+  }
 }

com/study/demo/test3_5.java

@@ -3,32 +3,32 @@ package com.study.demo;
 import java.util.Scanner;
 
 public class test3_5 {
-    public static void main(String[] args) {
-        Scanner scanner = new Scanner(System.in);
-        int n = scanner.nextInt();
-        int[] t = new int[n - 1];
-        int[] s = new int[n];
-        for (int i = 0; i < n - 1; i++) {
-            t[i] = scanner.nextInt();
-        }
-        for (int i = 0; i < n; i++) {
-            s[i] = scanner.nextInt();
-        }
-        int x = scanner.nextInt();
-        int y = scanner.nextInt();
-
-        int total = 0;
-        if (x < y) {
-            for (int i = x - 1; i < y - 1; i++) {
-                total += s[i] + t[i];
-            }
-            total += s[y - 1];
-        } else {
-            for (int i = x - 1; i >= y; i--) {
-                total += s[i] + (i > 0 ? t[i - 1] : 0);
-            }
-            total += s[y - 1];
-        }
-        System.out.println(total);
+  public static void main(String[] args) {
+    Scanner scanner = new Scanner(System.in);
+    int n = scanner.nextInt();
+    int[] t = new int[n - 1];
+    int[] s = new int[n];
+    for (int i = 0; i < n - 1; i++) {
+      t[i] = scanner.nextInt();
     }
+    for (int i = 0; i < n; i++) {
+      s[i] = scanner.nextInt();
+    }
+    int x = scanner.nextInt();
+    int y = scanner.nextInt();
+
+    int total = 0;
+    if (x < y) {
+      for (int i = x - 1; i < y - 1; i++) {
+        total += s[i] + t[i];
+      }
+      total += s[y - 1];
+    } else {
+      for (int i = x - 1; i >= y; i--) {
+        total += s[i] + (i > 0 ? t[i - 1] : 0);
+      }
+      total += s[y - 1];
+    }
+    System.out.println(total);
+  }
 }

com/study/demo2/Account.java

@@ -1,36 +1,36 @@
 package com.study.demo2;
 
 public class Account {
-    private String accountId;
-    private String owner;
-    private double balance;
+  private String accountId;
+  private String owner;
+  private double balance;
 
-    public Account(String accountId, String owner, double balance) {
-        this.accountId = accountId;
-        this.owner = owner;
-        this.balance = balance;
-    }
+  public Account(String accountId, String owner, double balance) {
+    this.accountId = accountId;
+    this.owner = owner;
+    this.balance = balance;
+  }
 
-    public void deposit(double amount) {
-        if (amount > 0) {
-            balance += amount;
-        }
+  public void deposit(double amount) {
+    if (amount > 0) {
+      balance += amount;
     }
+  }
 
-    public void withdraw(double amount) {
-        if (amount > 0 && amount <= balance) {
-            balance -= amount;
-        }
+  public void withdraw(double amount) {
+    if (amount > 0 && amount <= balance) {
+      balance -= amount;
     }
+  }
 
-    public void transfer(Account target, double amount) {
-        if (amount > 0 && amount <= balance) {
-            this.balance -= amount;
-            target.balance += amount;
-        }
+  public void transfer(Account target, double amount) {
+    if (amount > 0 && amount <= balance) {
+      this.balance -= amount;
+      target.balance += amount;
     }
+  }
 
-    public double getBalance() {
-        return balance;
-    }
-}
+  public double getBalance() {
+    return balance;
+  }
+}

com/study/demo2/Account_Main.java

@@ -1,15 +1,15 @@
 package com.study.demo2;
 
 public class Main {
-    public static void main(String[] args) {
-        Account acc1 = new Account("A001", "张三", 1000);
-        Account acc2 = new Account("A002", "李四", 500);
-        
-        acc1.deposit(200);
-        acc1.withdraw(100);
-        acc1.transfer(acc2, 300);
-        
-        System.out.println("账户1余额:" + acc1.getBalance());
-        System.out.println("账户2余额:" + acc2.getBalance());
-    }
-}
+  public static void main(String[] args) {
+    Account acc1 = new Account("A001", "张三", 1000);
+    Account acc2 = new Account("A002", "李四", 500);
+
+    acc1.deposit(200);
+    acc1.withdraw(100);
+    acc1.transfer(acc2, 300);
+
+    System.out.println("账户1余额:" + acc1.getBalance());
+    System.out.println("账户2余额:" + acc2.getBalance());
+  }
+}

com/study/demo2/Animal.java

@@ -1,44 +1,45 @@
 package com.study.demo2;
 
 public abstract class Animal {
-    protected String name;
+  protected String name;
 
-    public Animal(String name) {
-        this.name = name;
-    }
+  public Animal(String name) {
+    this.name = name;
+  }
 
-    public abstract void makeSound();
-    public abstract void move();
+  public abstract void makeSound();
+
+  public abstract void move();
 }
 
 class Dog extends Animal {
-    public Dog(String name) {
-        super(name);
-    }
+  public Dog(String name) {
+    super(name);
+  }
 
-    @Override
-    public void makeSound() {
-        System.out.println(name + " 汪汪叫");
-    }
+  @Override
+  public void makeSound() {
+    System.out.println(name + " 汪汪叫");
+  }
 
-    @Override
-    public void move() {
-        System.out.println(name + " 跑动");
-    }
+  @Override
+  public void move() {
+    System.out.println(name + " 跑动");
+  }
 }
 
 class Bird extends Animal {
-    public Bird(String name) {
-        super(name);
-    }
+  public Bird(String name) {
+    super(name);
+  }
 
-    @Override
-    public void makeSound() {
-        System.out.println(name + " 叽叽喳喳");
-    }
+  @Override
+  public void makeSound() {
+    System.out.println(name + " 叽叽喳喳");
+  }
 
-    @Override
-    public void move() {
-        System.out.println(name + " 飞翔");
-    }
-}
+  @Override
+  public void move() {
+    System.out.println(name + " 飞翔");
+  }
+}

com/study/demo2/Animal_Main.java

@@ -1,12 +1,12 @@
 package com.study.demo2;
 
 public class Main {
-    public static void main(String[] args) {
-        Animal dog = new Dog("Buddy");
-        Animal bird = new Bird("Tweety");
-        dog.makeSound();
-        dog.move();
-        bird.makeSound();
-        bird.move();
-    }
-}
+  public static void main(String[] args) {
+    Animal dog = new Dog("Buddy");
+    Animal bird = new Bird("Tweety");
+    dog.makeSound();
+    dog.move();
+    bird.makeSound();
+    bird.move();
+  }
+}

com/study/demo2/Rectangle.java

@@ -1,37 +1,38 @@
 package com.study.demo2;
 
 public class Rectangle {
-    private double width = 1.0;
-    private double height = 1.0;
+  private double width = 1.0;
+  private double height = 1.0;
 
-    public Rectangle() {}
+  public Rectangle() {
+  }
 
-    public Rectangle(double width, double height) {
-        this.width = width;
-        this.height = height;
-    }
+  public Rectangle(double width, double height) {
+    this.width = width;
+    this.height = height;
+  }
 
-    public double getArea() {
-        return width * height;
-    }
+  public double getArea() {
+    return width * height;
+  }
 
-    public double getPerimeter() {
-        return 2 * (width + height);
-    }
+  public double getPerimeter() {
+    return 2 * (width + height);
+  }
 
-    public double getWidth() {
-        return width;
-    }
+  public double getWidth() {
+    return width;
+  }
 
-    public void setWidth(double width) {
-        this.width = width;
-    }
+  public void setWidth(double width) {
+    this.width = width;
+  }
 
-    public double getHeight() {
-        return height;
-    }
+  public double getHeight() {
+    return height;
+  }
 
-    public void setHeight(double height) {
-        this.height = height;
-    }
+  public void setHeight(double height) {
+    this.height = height;
+  }
 }

com/study/demo2/Rectangle_Main.java

@@ -1,18 +1,18 @@
 package com.study.demo2;
 
 public class Main {
-    public static void main(String[] args) {
-        Rectangle rect1 = new Rectangle(5.0, 3.0);
-        System.out.println("面积:" + rect1.getArea());
-        System.out.println("周长:" + rect1.getPerimeter());
-        
-        Rectangle rect2 = new Rectangle();
-        System.out.println("默认面积:" + rect2.getArea());
-        System.out.println("默认周长:" + rect2.getPerimeter());
-        
-        rect2.setWidth(2.5);
-        rect2.setHeight(4.0);
-        System.out.println("修改后面积:" + rect2.getArea());
-        System.out.println("修改后周长:" + rect2.getPerimeter());
-    }
-}
+  public static void main(String[] args) {
+    Rectangle rect1 = new Rectangle(5.0, 3.0);
+    System.out.println("面积:" + rect1.getArea());
+    System.out.println("周长:" + rect1.getPerimeter());
+
+    Rectangle rect2 = new Rectangle();
+    System.out.println("默认面积:" + rect2.getArea());
+    System.out.println("默认周长:" + rect2.getPerimeter());
+
+    rect2.setWidth(2.5);
+    rect2.setHeight(4.0);
+    System.out.println("修改后面积:" + rect2.getArea());
+    System.out.println("修改后周长:" + rect2.getPerimeter());
+  }
+}

com/study/demo2/Student.java

@@ -1,40 +1,46 @@
 package com.study.demo2;
 
 public class Student {
-    private String id;
-    private String name;
-    private int[] score = new int[10];
+  private String id;
+  private String name;
+  private int[] score = new int[10];
 
-    public Student(String id, String name, int[] scores) {
-        this.id = id;
-        this.name = name;
-        if (scores.length == 10) {
-            this.score = scores;
-        }
+  public Student(String id, String name, int[] scores) {
+    this.id = id;
+    this.name = name;
+    if (scores.length == 10) {
+      this.score = scores;
     }
+  }
 
-    public double getAverage() {
-        int sum = 0;
-        for (int s : score) {
-            sum += s;
-        }
-        return (double) Math.round((sum / 10.0) * 100) / 100;
+  public double getAverage() {
+    int sum = 0;
+    for (int s : score) {
+      sum += s;
     }
+    return (double) Math.round((sum / 10.0) * 100) / 100;
+  }
 
-    public int getMaxScore() {
-        int max = score[0];
-        for (int s : score) {
-            if (s > max) max = s;
-        }
-        return max;
+  public int getMaxScore() {
+    int max = score[0];
+    for (int s : score) {
+      if (s > max)
+        max = s;
     }
+    return max;
+  }
 
-    public char getGrade() {
-        double avg = getAverage();
-        if (avg >= 90) return 'A';
-        else if (avg >= 80) return 'B';
-        else if (avg >= 70) return 'C';
-        else if (avg >= 60) return 'D';
-        else return 'E';
-    }
-}
+  public char getGrade() {
+    double avg = getAverage();
+    if (avg >= 90)
+      return 'A';
+    else if (avg >= 80)
+      return 'B';
+    else if (avg >= 70)
+      return 'C';
+    else if (avg >= 60)
+      return 'D';
+    else
+      return 'E';
+  }
+}

com/study/demo2/Student_Main.java

@@ -1,12 +1,11 @@
 package com.study.demo2;
 
 public class Main {
-    public static void main(String[] args) {
-        int[] scores = {85, 90, 78, 92, 88, 76, 95, 89, 79, 94};
-        Student student = new Student("5001", "张三", scores);
-        
-        System.out.println("平均分: " + student.getAverage());
-        System.out.println("最高分: " + student.getMaxScore());
-        System.out.println("等级: " + student.getGrade());
-    }
-}
+  public static void main(String[] args) {
+    int[] scores = { 85, 90, 78, 92, 88, 76, 95, 89, 79, 94 };
+    Student student = new Student("5001", "张三", scores);
+    System.out.println("平均分: " + student.getAverage());
+    System.out.println("最高分: " + student.getMaxScore());
+    System.out.println("等级: " + student.getGrade());
+  }
+}

com/study/demo4/AlipayPayment.java

@@ -0,0 +1,9 @@
+package com.study.demo4;
+
+class AlipayPayment implements PaymentProcessor {
+  @Override
+  public boolean pay(double amount) {
+    System.out.println("支付宝支付: " + amount);
+    return true;
+  }
+}

com/study/demo4/BikeDeliveryCalculator.java

@@ -0,0 +1,11 @@
+package com.study.demo4;
+
+class BikeDeliveryCalculator implements DeliveryFeeCalculator {
+  @Override
+  public double calculateFee(double distance) {
+    if (distance <= 5) {
+      return 5.0; // 起步价
+    }
+    return 5.0 + (distance - 5) * 1.5;
+  }
+}

com/study/demo4/Cardeliverycalculator.java

@@ -0,0 +1,12 @@
+package com.study.demo4;
+
+class CarDeliveryCalculator implements DeliveryFeeCalculator {
+  @Override
+  public double calculateFee(double distance) {
+    if (distance <= 5) {
+      return 10.0; // 起步价
+    }
+    return 10.0 + (distance - 5) * 2.0;
+  }
+}
+

com/study/demo4/CreditCardPayment.java

@@ -0,0 +1,9 @@
+package com.study.demo4;
+
+class CreditCardPayment implements PaymentProcessor {
+  @Override
+  public boolean pay(double amount) {
+    System.out.println("银行卡支付: " + amount);
+    return true;
+  }
+}

com/study/demo4/DeliveryFeeCalculator.java

@@ -0,0 +1,5 @@
+package com.study.demo4;
+
+interface DeliveryFeeCalculator {
+  double calculateFee(double distance);
+}

com/study/demo4/HomeAppliance.java

@@ -0,0 +1,26 @@
+package com.study.demo4;
+
+abstract class HomeAppliance implements SmartDevice {
+  protected String name;
+  protected boolean isOn;
+
+  public HomeAppliance(String name) {
+    this.name = name;
+    this.isOn = false;
+  }
+
+  @Override
+  public void turnOn() {
+    isOn = true;
+  }
+
+  @Override
+  public void turnOff() {
+    isOn = false;
+  }
+
+  @Override
+  public String getStatus() {
+    return name + " is " + (isOn ? "ON" : "OFF");
+  }
+}

com/study/demo4/HomeController.java

@@ -0,0 +1,21 @@
+package com.study.demo4;
+
+import java.util.ArrayList;
+import java.util.List;
+
+class HomeController {
+  private List<SmartDevice> devices = new ArrayList<>();
+
+  public void addDevice(SmartDevice device) {
+    devices.add(device);
+  }
+
+  public String getDeviceStatus(String name) {
+    for (SmartDevice device : devices) {
+      if (device.getStatus().contains(name)) {
+        return device.getStatus();
+      }
+    }
+    return "Device not found";
+  }
+}

com/study/demo4/PaymentFactory.java

@@ -0,0 +1,16 @@
+package com.study.demo4;
+
+class PaymentFactory {
+  public static PaymentProcessor getProcessor(String type) {
+    switch (type.toLowerCase()) {
+      case "wechat":
+        return new WechatPayment();
+      case "alipay":
+        return new AlipayPayment();
+      case "card":
+        return new CreditCardPayment();
+      default:
+        throw new IllegalArgumentException("不支持的支付方式");
+    }
+  }
+}

com/study/demo4/PaymentProcessor.java

@@ -0,0 +1,6 @@
+package com.study.demo4;
+
+interface PaymentProcessor {
+  boolean pay(double amount);
+}
+

com/study/demo4/SmartAirConditioner.java

@@ -0,0 +1,7 @@
+package com.study.demo4;
+
+class SmartAirConditioner extends HomeAppliance {
+  public SmartAirConditioner(String name) {
+    super(name);
+  }
+}

com/study/demo4/SmartDevice.java

@@ -0,0 +1,7 @@
+package com.study.demo4;
+
+interface SmartDevice {
+  void turnOn();
+  void turnOff();
+  String getStatus();
+}

com/study/demo4/SmartLight.java

@@ -0,0 +1,7 @@
+package com.study.demo4;
+
+class SmartLight extends HomeAppliance {
+  public SmartLight(String name) {
+    super(name);
+  }
+}

com/study/demo4/SmartMasher.java

@@ -0,0 +1,7 @@
+package com.study.demo4;
+
+class SmartMasher extends HomeAppliance {
+  public SmartMasher(String name) {
+    super(name);
+  }
+}

com/study/demo4/TestControl.java

@@ -0,0 +1,31 @@
+package com.study.demo4;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class TestControl {
+  public static void main(String[] args) {
+    HomeController controller = new HomeController();
+
+    // 创建设备
+    SmartLight light = new SmartLight("Living Room Light");
+    SmartAirConditioner ac = new SmartAirConditioner("Bedroom AC");
+    SmartMasher masher = new SmartMasher("Kitchen Masher");
+
+    // 添加到控制器
+    controller.addDevice(light);
+    controller.addDevice(ac);
+    controller.addDevice(masher);
+
+    // 测试设备状态
+    light.turnOff();
+    ac.turnOff();
+    masher.turnOn();
+
+    // 查询状态
+    System.out.println(controller.getDeviceStatus("Living Room Light"));
+    System.out.println(controller.getDeviceStatus("Bedroom AC"));
+    System.out.println(controller.getDeviceStatus("Kitchen Masher"));
+    System.out.println(controller.getDeviceStatus("Non-existent Device"));
+  }
+}

com/study/demo4/TestPay.java

@@ -0,0 +1,8 @@
+package com.study.demo4;
+
+public class TestPay {
+  public static void main(String[] args) {
+    PaymentProcessor processor = PaymentFactory.getProcessor("alipay");
+    processor.pay(666.0);
+  }
+}

com/study/demo4/TestTransport.java

@@ -0,0 +1,22 @@
+package com.study.demo4;
+
+public class TestTransport {
+  public static void main(String[] args) {
+    // 测试自行车配送
+    DeliveryFeeCalculator bike = new BikeDeliveryCalculator();
+    System.out.println("自行车配送 3km: ¥" + bike.calculateFee(3));
+    System.out.println("自行车配送 8km: ¥" + bike.calculateFee(8));
+
+    // 测试汽车配送
+    DeliveryFeeCalculator car = new CarDeliveryCalculator();
+    System.out.println("汽车配送 3km: ¥" + car.calculateFee(3));
+    System.out.println("汽车配送 8km: ¥" + car.calculateFee(8));
+
+    // 对比不同距离的费用
+    System.out.println("\n费用对比:");
+    for (int km = 1; km <= 10; km++) {
+      System.out.printf("%dkm: 自行车¥%.1f, 汽车¥%.1f%n",
+          km, bike.calculateFee(km), car.calculateFee(km));
+    }
+  }
+}

com/study/demo4/WechatPayment.java

@@ -0,0 +1,9 @@
+package com.study.demo4;
+
+class WechatPayment implements PaymentProcessor {
+  @Override
+  public boolean pay(double amount) {
+    System.out.println("微信支付: " + amount);
+    return true;
+  }
+}

com/study/demo5/DataIO.java

@@ -0,0 +1,40 @@
+package com.study.demo5;
+
+import java.io.*;
+
+public class DataIO {
+  public void writeConfig(String path) {
+    try (DataOutputStream dos = new DataOutputStream(
+        new FileOutputStream(path))) {
+
+      dos.writeUTF("李华"); // 用户名
+      dos.writeInt(25); // 年龄
+      dos.writeBoolean(true); // 是否启用
+      dos.writeDouble(1234.56); // 余额
+
+      System.out.println("配置写入成功: " + path);
+
+    } catch (IOException e) {
+      System.err.println("写入配置失败: " + e.getMessage());
+    }
+  }
+
+  public void readConfig(String path) {
+    try (DataInputStream dis = new DataInputStream(
+        new FileInputStream(path))) {
+
+      String username = dis.readUTF();
+      int age = dis.readInt();
+      boolean enabled = dis.readBoolean();
+      double balance = dis.readDouble();
+
+      System.out.println("用户名: " + username);
+      System.out.println("年龄: " + age);
+      System.out.println("是否启用: " + enabled);
+      System.out.println("余额: " + balance);
+
+    } catch (IOException e) {
+      System.err.println("读取配置失败: " + e.getMessage());
+    }
+  }
+}

com/study/demo5/FileCopy.java

@@ -0,0 +1,20 @@
+package com.study.demo5;
+
+import java.io.*;
+
+public class FileCopy {
+  public void copy(String source, String target) {
+    try (FileInputStream fis = new FileInputStream(source);
+        FileOutputStream fos = new FileOutputStream(target)) {
+      byte[] buffer = new byte[1024];
+      int bytesRead;
+      while ((bytesRead = fis.read(buffer)) != -1) {
+        fos.write(buffer, 0, bytesRead);
+      }
+    } catch (FileNotFoundException e) {
+      System.err.println("源文件未找到: " + e.getMessage());
+    } catch (IOException e) {
+      System.err.println("文件复制失败: " + e.getMessage());
+    }
+  }
+}

com/study/demo5/FileStat.java

@@ -0,0 +1,25 @@
+package com.study.demo5;
+
+import java.io.*;
+
+public class FileStat {
+  public long countBytes(String filePath) {
+    long totalBytes = 0;
+
+    try (FileInputStream fis = new FileInputStream(filePath)) {
+
+      byte[] buffer = new byte[1024];
+      int bytesRead;
+
+      while ((bytesRead = fis.read(buffer)) != -1) {
+        totalBytes += bytesRead;
+      }
+
+    } catch (IOException e) {
+      System.err.println("文件读取失败: " + e.getMessage());
+      return -1;
+    }
+
+    return totalBytes;
+  }
+}

com/study/demo5/Main.java

@@ -0,0 +1,17 @@
+package com.study.demo5;
+
+ public class Main {
+    public static void main(String[] args) {
+        // 7.1 测试
+        FileCopy fc = new FileCopy();
+        fc.copy("source.txt", "target.txt");
+        // 7.2 测试
+        DataIO dataIO = new DataIO();
+        dataIO.writeConfig("config.bin");
+        dataIO.readConfig("config.bin");
+        // 7.3 测试
+        FileStat fs = new FileStat();
+        long size = fs.countBytes("test3.txt");
+        System.out.println("文件大小: " + size + " 字节");
+    }
+}

com/study/demo6/SumThread.java

@@ -0,0 +1,52 @@
+package com.study.demo6;
+
+public class SumThread {
+  static class PartSumTask implements Runnable {
+    private final int[] array;
+    private final int start;
+    private final int end;
+    public long result;
+
+    public PartSumTask(int[] array, int start, int end) {
+      this.array = array;
+      this.start = start;
+      this.end = end;
+    }
+
+    @Override
+    public void run() {
+      long sum = 0;
+      for (int i = start; i <= end; i++) {
+        sum += array[i];
+      }
+      result = sum;
+    }
+  }
+
+  public static void main(String[] args) throws InterruptedException {
+    int size = 1_000_000;
+    int[] array = new int[size];
+    for (int i = 0; i < size; i++) {
+      array[i] = i;
+    }
+
+    PartSumTask task1 = new PartSumTask(array, 0, 333_333);
+    PartSumTask task2 = new PartSumTask(array, 333_334, 666_666);
+    PartSumTask task3 = new PartSumTask(array, 666_667, 999_999);
+
+    Thread t1 = new Thread(task1);
+    Thread t2 = new Thread(task2);
+    Thread t3 = new Thread(task3);
+
+    t1.start();
+    t2.start();
+    t3.start();
+
+    t1.join();
+    t2.join();
+    t3.join();
+
+    long total = task1.result + task2.result + task3.result;
+    System.out.println("总和为：" + total);
+  }
+}

com/study/demo6/ThreadDemo1.java

@@ -0,0 +1,20 @@
+package com.study.demo6;
+
+public class ThreadDemo1 {
+  static class MyThread extends Thread {
+    @Override
+    public void run() {
+      for (int i = 1; i <= 5; i++) {
+        System.out.println("当前线程：" + getName() + "，输出次数 " + i);
+      }
+    }
+  }
+
+  public static void main(String[] args) {
+    MyThread s1 = new MyThread();
+    MyThread s2 = new MyThread();
+
+    s1.start();
+    s2.start();
+  }
+}

com/study/demo6/ThreadDemo2.java

@@ -0,0 +1,22 @@
+package com.study.demo6;
+
+public class ThreadDemo2 {
+  static class CountTask implements Runnable {
+    @Override
+    public void run() {
+      for (int i = 1; i <= 10; i++) {
+        System.out.println(Thread.currentThread().getName() + " 计数：" + i);
+        try {
+          Thread.sleep(500);
+        } catch (InterruptedException e) {
+          e.printStackTrace();
+        }
+      }
+    }
+  }
+
+  public static void main(String[] args) {
+    Thread t = new Thread(new CountTask(), "计数线程");
+    t.start();
+  }
+}

flake.nix

@@ -3,7 +3,7 @@
   inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
   outputs = { self, nixpkgs }:
   let
-    supportedSystems = [ "x86_64-linux" "aarch64-linux" ];
+    supportedSystems = [ "x86_64-linux" ];
     forEachSupportedSystem = f: nixpkgs.lib.genAttrs supportedSystems (system: f {
       pkgs = import nixpkgs { inherit self system; };
     });