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Using composite ordering to fix the problem #253

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Using composite ordering to fix the problem #253

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15 changes: 8 additions & 7 deletions src/main/java/com/github/hcsp/polymorphism/User.java
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Original file line number Diff line number Diff line change
@@ -1,9 +1,6 @@
package com.github.hcsp.polymorphism;

import java.util.Arrays;
import java.util.List;
import java.util.Objects;
import java.util.TreeSet;
import java.util.*;

public class User implements Comparable<User> {
/** 用户ID，数据库主键，全局唯一 */
Expand All @@ -12,7 +9,7 @@ public class User implements Comparable<User> {
/** 用户名 */
private final String name;

public User(Integer id, String name) {
public User(Integer id, String name) { // 构造器
this.id = id;
this.name = name;
}
Expand Down Expand Up @@ -47,7 +44,11 @@ public int hashCode() {
/** 老板说让我按照用户名排序 */
@Override
public int compareTo(User o) {
return name.compareTo(o.name);
int nameCompare = name.compareTo(o.getName());
if (nameCompare != 0) {
return nameCompare; // name 不同：按 name 排序
}
return id.compareTo(o.getId()); // name 相同：按 id 排序（避免被当作重复）
}

public static void main(String[] args) {
Expand All @@ -57,8 +58,8 @@ public static void main(String[] args) {
new User(10, "z"),
new User(1, "a"),
new User(2000, "a"));

TreeSet<User> treeSet = new TreeSet<>(users);
// 为什么这里的输出是3？试着修复其中的bug
System.out.println(treeSet.size());
}
}