大家好,我从来没有写过比较器 b4,我遇到了一个真正的问题。我创建了一个哈希表。
Hashtable <String, Objects> ht;
有人可以展示如何为 Hashtable 编写比较器吗?我见过的例子超越了等于和一切,但我根本不知道。下面的代码不是我的,而是我发现的一个例子,哈希表中的关键是我猜我不能这样做。
public class Comparator implements Comparable<Name> {
private final String firstName, lastName;
public void Name(String firstName, String lastName) {
if (firstName == null || lastName == null)
throw new NullPointerException();
this.firstName = firstName;
this.lastName = lastName;
}
public String firstName() { return firstName; }
public String lastName() { return lastName; }
public boolean equals(Object o) {
if (!(o instanceof Name))
return false;
Name n = (Name)o;
return n.firstName.equals(firstName) &&
n.lastName.equals(lastName);
}
public int hashCode() {
return 31*firstName.hashCode() + lastName.hashCode();
}
public String toString() {
return firstName + " " + lastName;
}
public int compareTo(Name n) {
int lastCmp = lastName.compareTo(n.lastName);
return (lastCmp != 0 ? lastCmp :
firstName.compareTo(n.firstName));
}
}