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TreeMapTest.java
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145 lines (124 loc) · 3.86 KB
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import org.junit.Test;
import java.util.*;
/**
* @ Description:
* @ Author: Jay
* @ Date: Create in 19:56 2021/4/15
* @ Version:
*/
public class TreeMapTest {
//自然排序
@Test
public void TreeMapTest1() {
TreeMap map = new TreeMap();
User u1 = new User("Tom", 23);
User u2 = new User("Tom", 24);
User u3 = new User("Marry", 23);
User u4 = new User("Jack", 23);
User u5 = new User("Rose", 24);
map.put(u1, 98);
map.put(u2, 89);
map.put(u3, 76);
map.put(u4, 100);
map.put(u5, 45);
//遍历
Set entryMap = map.entrySet();
Iterator iterator = entryMap.iterator();
while (iterator.hasNext()) {
Object obj = iterator.next();
Map.Entry entry = (Map.Entry) obj;
System.out.println(entry.getKey() + "--->" + entry.getValue());
}
}
//定制排序：重写了compare方法后，比较key是否相等时就会调用compare比较
//下面例子中，compare()只涉及age属性，所以插入时年龄相同的对象会被当做key相同
@Test
public void TreeMapTest2() {
TreeMap map = new TreeMap(new Comparator() {
@Override
public int compare(Object o1, Object o2) {
if (o1 instanceof User && o2 instanceof User) {
User u1 = (User) o1;
User u2 = (User) o2;
return Integer.compare(u1.getAge(), u2.getAge());
}
throw new RuntimeException("类型不匹配");
}
});
User u1 = new User("Tom", 23);
User u2 = new User("Jerry", 23);
User u3 = new User("Marry", 23);
User u4 = new User("Tom", 26);
User u5 = new User("Rose", 24);
map.put(u1, 98);
map.put(u2, 89);//无法插入，因为年龄相同，compare()返回0
map.put(u3, 76);//修改了u1的value值为76
map.put(u4, 100);//年龄不同，不同key
map.put(u5, 45);
//遍历
Set entryMap = map.entrySet();
Iterator iterator = entryMap.iterator();
while (iterator.hasNext()) {
Object obj = iterator.next();
Map.Entry entry = (Map.Entry) obj;
System.out.println(entry.getKey() + "--->" + entry.getValue());
}
}
}
class User implements Comparable {
private String name;
private int age;
public User() {
}
public User(String name, int age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
User user = (User) o;
if (age != user.age) return false;
return name != null ? name.equals(user.name) : user.name == null;
}
@Override
public String toString() {
return "User{" +
"name='" + name + '\'' +
", age=" + age +
'}';
}
@Override
public int hashCode() {
int result = name != null ? name.hashCode() : 0;
result = 31 * result + age;
return result;
}
//按照姓名从大到小，年龄从小到大
@Override
public int compareTo(Object o) {
if (o instanceof User) {
User user = (User) o;
int compare = -this.name.compareTo(user.name);
if (compare != 0) {
return compare;
} else {
return Integer.compare(this.age, user.age);
}
}
throw new RuntimeException("类型不匹配");
}
}