1、Comparable
Comparable是内部比较器（即用于实现了Comparable接口的类与自身进行比较），称自然排序；
至于一个类与实现了Comparable接口的另一个类的比较则依赖于CompareTo方法的实现。
返回值有3个
/**
* @Author AlexanderBai
* @data 2019/3/14 15:20
*/
public class Domain implements Comparable<Domain> {
private String str;
public Domain(String str) {
this.str = str;
}
public String getStr() {
return str;
}
public void setStr(String str) {
this.str = str;
}
@Override
public int compareTo(Domain domain) {
if (this.str.compareTo(domain.str)>0) {
return 1;
}
else if (this.str.compareTo(domain.str) == 0) {
return 0;
}
else
return -1;
}
public static void main(String[] args) {
Domain domain = new Domain("a");
Domain domain1 = new Domain("a");
Domain domain2 = new Domain("B");
Domain domain3 = new Domain("c");
System.out.println("domain.compareTo(domain1) = " + domain.compareTo(domain1));
System.out.println("domain.compareTo(domain2) = " + domain.compareTo(domain2));
System.out.println("domain2.compareTo(domain3) = " + domain2.compareTo(domain3));
}
}
运行结果：
domain.compareTo(domain1) = 0 domain.compareTo(domain2) = 1 domain2.compareTo(domain3) = -1
1.1、基于Comparable实现的二叉树操作
Comparable比较器的排序过程是二叉树的排序方法，再利用中序遍历依次读取
package testfile;
/**
* @Author AlexanderBai
* @data 2019/3/14 15:52
*/
class BinaryTree{
class Node{
private Comparable data;
private Node left;
private Node right;
/**
* 添加子节点
* @param newNode
*/
public void addNode(Node newNode) {
if (newNode.data.compareTo(this.data)<0) {
if (this.left == null) {
this.left=newNode;
}else {
this.left.addNode(newNode);
}
}
if (newNode.data.compareTo(this.data)>=0){
if (this.right == null) {
this.right = newNode;
}else {
this.right.addNode(newNode);
}
}
}
//中序遍历输出
public void printNode() {
if (this.left != null) {
this.left.printNode();
}
System.out.println(this.data+"\t");
if (this.right != null) {
this.right.printNode();
}
}
}
private Node root;
/**
* 添加根节点
* @param data
*/
public void add(Comparable data) {
Node newNode=new Node();
newNode.data=data;
if (root == null) {
root=newNode;
}else {
root.addNode(newNode);
}
}
public void print() {
this.root.printNode();
}
}
public class Test {
public static void main(String[] args) {
BinaryTree binaryTree=new BinaryTree();
binaryTree.add(8);
binaryTree.add(87);
binaryTree.add(2456);
binaryTree.add(76);
binaryTree.add(1);
binaryTree.add(44);
System.out.println("排序之后的结果是：");
binaryTree.print();
}
}
运行结果
2、Comparator
一般在两种情况下使用Comparator
①、不支持自己和自己比较
②、对自然排序方法ComparaTo不满意，自己重写
假设对以上的ComparaTo方法不满意,DoMian类不变
/**
* @Author AlexanderBai
* @data 2019/3/14 17:30
*/
public class TestComparator implements Comparator<Domain> {
@Override
public int compare(Domain domain1, Domain domain2) {
if (domain1.getStr().compareTo(domain2.getStr()) > 0) {
return 1;
}
else if (domain1.getStr().compareTo(domain2.getStr()) == 0){
return 0;
}
else
return -1;
}
public static void main(String[] args) {
Domain domain = new Domain("a");
Domain domain1 = new Domain("a");
Domain domain2 = new Domain("B");
Domain domain3 = new Domain("c");
TestComparator testComparator=new TestComparator();
System.out.println("testComparator.compare(domain,domain1) = " + testComparator.compare(domain, domain1));
System.out.println("testComparator.compare(domain,domain2) = " + testComparator.compare(domain1, domain2));
System.out.println("testComparator.compare(domain2,domain3) = " + testComparator.compare(domain2, domain3));
}
}
运行结果：
testComparator.compare(domain,domain1) = 0 testComparator.compare(domain,domain2) = 1 testComparator.compare(domain2,domain3) = -1
