import com.sun.corba.se.impl.orb.ParserTable;
import org.junit.Test;
import java.util.Arrays;
import java.util.Comparator;
/**
* 对象比较大小
* 一:说明:Java中的对象,正常情况下,只能进行比较:== 或!=。不能使用 > 或 <的
* 但是在开发场景中,我们需要对多个对象进行排序,言外之意,就需要比较对象的大小。
* 如何实现?使用接口中的任意一个:Comparable(自然排序)或Comparator(定制排序)
* <p>
* 二:Comparable接口和Comparator的使用对比
* Comparable的实现对象在任何位置都可以比较大小
* Comparator接口属于临时比较
*
* @author: qyx
* @date: 2022-07-30 21:45
* @desc:
*/
public class CompareTest {
/*
Comparable使用举例
像String和包装类重写了Comparable的compareTo方法
正数 大于,负数 小于,0 等于
自定义的类要实现Comparable接口,重写compareTo方法
*/
@Test
public void test1() {
String[] arr = new String[]{"AA", "CC", "KK", "MM", "GG", "JJ", "DD"};
Arrays.sort(arr);
System.out.println(Arrays.toString(arr));
}
@Test
public void test2() {
Goods[] arr = new Goods[4];
arr[0] = new Goods("联想鼠标", 34);
arr[1] = new Goods("戴尔鼠标", 43);
arr[2] = new Goods("小米鼠标", 12);
arr[3] = new Goods("华为鼠标", 65);
Arrays.sort(arr);
System.out.println(Arrays.toString(arr));
}
/*
Comparator接口的使用:定制排序
*/
@Test
public void test3() {
String[] arr = new String[]{"AA", "CC", "KK", "MM", "GG", "JJ", "DD"};
Arrays.sort(arr, new Comparator<String>() {
//按照字符串从大到小的顺序排列
@Override
public int compare(String o1, String o2) {
if (o1 instanceof String && o2 instanceof String) {
String s1 = (String) o1;
String s2 = (String) o2;
return -s1.compareTo(s2);
}
throw new RuntimeException("输入的数据类型不一致");
}
});
System.out.println(Arrays.toString(arr));
}
@Test
public void test4() {
Goods[] arr = new Goods[5];
arr[0] = new Goods("lenovo", 34);
arr[1] = new Goods("dell", 43);
arr[2] = new Goods("xiaomi", 12);
arr[3] = new Goods("huawei", 65);
arr[4] = new Goods("huawei", 45);
Arrays.sort(arr, new Comparator<Goods>() {
//按照字符串从大到小的顺序排列
@Override
public int compare(Goods o1, Goods o2) {
if (o1 instanceof Goods && o2 instanceof Goods) {
Goods s1 = (Goods) o1;
Goods s2 = (Goods) o2;
if(s1.getName().equals(s2.getName())){
return -Double.compare(o1.getPrice(),o2.getPrice());
}else return s1.getName().compareTo(s2.getName());
}
throw new RuntimeException("输入的数据类型不一致");
}
});
System.out.println(Arrays.toString(arr));
}
}
/**
* 商品类
* @author: qyx
* @date: 2022-07-30 22:33
* @desc:
*/
public class Goods implements Comparable{
private String name;
private double price;
public Goods() {
}
public Goods(String name, double price) {
this.name = name;
this.price = price;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public double getPrice() {
return price;
}
public void setPrice(double price) {
this.price = price;
}
@Override
public String toString() {
return "Goods{" + "name='" + name + '\'' + ", price=" + price + '}';
}
//指明商品比较大小的方式:按照价格从低到高排序
@Override
public int compareTo(Object o) {
if(this == o){
return 0;
}
if(o instanceof Goods){
Goods goods = (Goods) o;
if(this.price > goods.price){
return 1;
}else if (this.price < goods.price){
return -1;
}else {
return 0;
}
}
throw new RuntimeException("传入的数据类型不一致");
}
}