TreeSet是以自然顺序存的数据,例如
Set<Student> students=new TreeSet(); students.add(new Student("111")); students.add(new Student("333")); students.add(new Student("222")); for (Student student : students) { System.out.println(student.getId()); }
输出结果为111 222 333
而且这时候的Student必须继承Comparable接口,重写抽象方法CompareTo方法
public class Student implements Comparable<Student> { private String id; public Student(String id) { this.id = id; } @Override public int compareTo(Student o) { return 1; } }
出现这样的效果是因为存储的时候的代码是这样的
public V put(K key, V value) { Entry<K,V> t = root; if (t == null) { compare(key, key); // type (and possibly null) check root = new Entry<>(key, value, null); size = 1; modCount++; return null; } int cmp; Entry<K,V> parent; // split comparator and comparable paths Comparator<? super K> cpr = comparator; if (cpr != null) { do { parent = t; cmp = cpr.compare(key, t.key); if (cmp < 0) t = t.left; else if (cmp > 0) t = t.right; else return t.setValue(value); } while (t != null); } else { if (key == null) throw new NullPointerException(); @SuppressWarnings("unchecked") Comparable<? super K> k = (Comparable<? super K>) key; do { parent = t; cmp = k.compareTo(t.key); if (cmp < 0) t = t.left; else if (cmp > 0) t = t.right; else return t.setValue(value); } while (t != null); } Entry<K,V> e = new Entry<>(key, value, parent); if (cmp < 0) parent.left = e; else parent.right = e; fixAfterInsertion(e); size++; modCount++; return null; }
看红色的代码,存储的时候执行compareTo方法,这个时候就会判断你存的值得大小顺序,然后判断你该存储的顺序,就是自然顺序了。。
原文地址:https://www.cnblogs.com/lyxcode/p/9467257.html
时间: 2024-11-05 16:07:43