diff --git a/Certificate.java b/Certificate.java
new file mode 100644
index 0000000..d7d7c41
--- /dev/null
+++ b/Certificate.java
@@ -0,0 +1,173 @@
+import java.time.LocalDate;
+import java.util.Objects;
+import java.util.UUID;
+
+/**
+ * 证书类：管理员工获得的证书
+ */
+public class Certificate {
+    private String certificateId;     // 证书ID
+    private int employeeId;           // 员工ID
+    private String title;             // 证书名称
+    private String issuingAuthority;  // 发证机构
+    private LocalDate issueDate;      // 颁发日期
+    private LocalDate expiryDate;     // 到期日期（可选）
+    private String description;       // 证书描述
+    private String certificateUrl;    // 证书电子版URL（可选）
+    private boolean isActive;         // 是否有效
+    
+    /**
+     * 构造函数
+     */
+    public Certificate(int employeeId, String title, String issuingAuthority, 
+                      LocalDate issueDate) {
+        validateEmployeeId(employeeId);
+        validateTitle(title);
+        validateIssuingAuthority(issuingAuthority);
+        validateIssueDate(issueDate);
+        
+        this.certificateId = generateCertificateId();
+        this.employeeId = employeeId;
+        this.title = title;
+        this.issuingAuthority = issuingAuthority;
+        this.issueDate = issueDate;
+        this.isActive = true;  // 默认为有效证书
+        this.description = "";
+        this.certificateUrl = null;
+    }
+    
+    /**
+     * 构造函数（包含到期日期）
+     */
+    public Certificate(int employeeId, String title, String issuingAuthority, 
+                      LocalDate issueDate, LocalDate expiryDate) {
+        this(employeeId, title, issuingAuthority, issueDate);
+        
+        if (expiryDate != null && expiryDate.isBefore(issueDate)) {
+            throw new IllegalArgumentException("到期日期不能早于颁发日期");
+        }
+        this.expiryDate = expiryDate;
+        
+        // 如果有到期日期且已过期，则标记为无效
+        if (expiryDate != null && expiryDate.isBefore(LocalDate.now())) {
+            this.isActive = false;
+        }
+    }
+    
+    // 生成证书ID
+    private String generateCertificateId() {
+        return "CERT-" + UUID.randomUUID().toString().substring(0, 8).toUpperCase();
+    }
+    
+    // 验证方法
+    private void validateEmployeeId(int employeeId) {
+        if (employeeId <= 0) {
+            throw new IllegalArgumentException("员工ID必须为正整数");
+        }
+    }
+    
+    private void validateTitle(String title) {
+        if (title == null || title.trim().isEmpty()) {
+            throw new IllegalArgumentException("证书名称不能为空");
+        }
+    }
+    
+    private void validateIssuingAuthority(String issuingAuthority) {
+        if (issuingAuthority == null || issuingAuthority.trim().isEmpty()) {
+            throw new IllegalArgumentException("发证机构不能为空");
+        }
+    }
+    
+    private void validateIssueDate(LocalDate issueDate) {
+        if (issueDate == null || issueDate.isAfter(LocalDate.now())) {
+            throw new IllegalArgumentException("颁发日期不能晚于当前日期");
+        }
+    }
+    
+    /**
+     * 检查证书是否过期
+     */
+    public boolean isExpired() {
+        return expiryDate != null && expiryDate.isBefore(LocalDate.now());
+    }
+    
+    /**
+     * 检查证书是否仍然有效
+     */
+    public boolean isValid() {
+        return isActive && !isExpired();
+    }
+    
+    /**
+     * 更新证书到期日期
+     */
+    public void updateExpiryDate(LocalDate expiryDate) {
+        if (expiryDate != null && expiryDate.isBefore(issueDate)) {
+            throw new IllegalArgumentException("到期日期不能早于颁发日期");
+        }
+        this.expiryDate = expiryDate;
+        
+        // 更新状态
+        if (expiryDate != null && expiryDate.isBefore(LocalDate.now())) {
+            this.isActive = false;
+        }
+    }
+    
+    // Getter方法
+    public String getCertificateId() { return certificateId; }
+    public int getEmployeeId() { return employeeId; }
+    public String getTitle() { return title; }
+    public String getIssuingAuthority() { return issuingAuthority; }
+    public LocalDate getIssueDate() { return issueDate; }
+    public LocalDate getExpiryDate() { return expiryDate; }
+    public String getDescription() { return description; }
+    public String getCertificateUrl() { return certificateUrl; }
+    public boolean isActive() { return isActive; }
+    
+    // Setter方法
+    public void setTitle(String title) {
+        validateTitle(title);
+        this.title = title;
+    }
+    
+    public void setIssuingAuthority(String issuingAuthority) {
+        validateIssuingAuthority(issuingAuthority);
+        this.issuingAuthority = issuingAuthority;
+    }
+    
+    public void setDescription(String description) {
+        this.description = description != null ? description : "";
+    }
+    
+    public void setCertificateUrl(String certificateUrl) {
+        this.certificateUrl = certificateUrl;
+    }
+    
+    public void activate() {
+        this.isActive = true;
+    }
+    
+    public void deactivate() {
+        this.isActive = false;
+    }
+    
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Certificate that = (Certificate) o;
+        return certificateId.equals(that.certificateId);
+    }
+    
+    @Override
+    public int hashCode() {
+        return Objects.hash(certificateId);
+    }
+    
+    @Override
+    public String toString() {
+        return String.format("证书[ID: %s, 名称: %s, 员工ID: %d, 发证机构: %s, 状态: %s]",
+                certificateId, title, employeeId, issuingAuthority, 
+                isValid() ? "有效" : "无效");
+    }
+}
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