Comparable和Comparator区别

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 {
 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 {
​
 @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