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更新時(shí)間：2021-05-06 11:39:30 來源：動(dòng)力節(jié)點(diǎn) 瀏覽886次
(1)軟件開發(fā)過程中集合排序是比較強(qiáng)大的功能，會使用集合Map、Set、List實(shí)現(xiàn)排序功能，知道匿名內(nèi)部類Comparator很關(guān)鍵，搞清楚集合排序的性能開銷，排序遇到的坑以及解決的方法，注意下面的例子都是JDK1.8的用法。
(1)UML類圖
(2)重點(diǎn)分析下ArrayList的排序，畢竟實(shí)戰(zhàn)開發(fā)用的最頻繁的就是它了
介紹：這種叫定制排序,或自定義排序,需編寫匿名內(nèi)部類,先new一個(gè)Comparator接口的比較器對象c,同時(shí)實(shí)現(xiàn)compare()其方法;
然后將比較器對象c傳給Collections.sort()方法的參數(shù)列表中,實(shí)現(xiàn)排序功能;一般用這種的比較多。
(1)實(shí)體類(private int id)
public class Person{
private int id;
private String name;
private String address;
public Person(int id, String name, String address) {
this.id = id;
this.name = name;
this.address = address;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "Person{" +
"id='" + id + '\'' +
", name='" + name + '\'' +
", address='" + address + '\'' +
'}';
}
}
(2)測試類
public class ArrayListTest {
public static void main(String[] args) {
List<Person> list=Lists.newArrayList();
//產(chǎn)生10以內(nèi)的隨機(jī)數(shù)
int num = (int)(Math.random()*1000+1);
for(int i=num;i>0;i--){
list.add(new Person(i,"張三","河南"));
}
for(Object o : list){
System.out.println(o);
}
System.out.println("++++++++++++++++++++++++++++++++++++");
Collections.sort(list, new Comparator<Person>() {
@Override
public int compare(Person o1, Person o2) {
if (o1.getId() > o2.getId()) {
return 1;
} else if (o1.getId() < o2.getId()) {
return -1;
}
return 0;
}
});
for(Object o : list){
System.out.println(o);
}
}
}
(3)結(jié)果(升序)
Person{id='10', name='張三', address='河南'}
Person{id='9', name='張三', address='河南'}
Person{id='8', name='張三', address='河南'}
Person{id='7', name='張三', address='河南'}
Person{id='6', name='張三', address='河南'}
Person{id='5', name='張三', address='河南'}
Person{id='4', name='張三', address='河南'}
Person{id='3', name='張三', address='河南'}
Person{id='2', name='張三', address='河南'}
Person{id='1', name='張三', address='河南'}
++++++++++++++++++++++++++++++++++++
Person{id='1', name='張三', address='河南'}
Person{id='2', name='張三', address='河南'}
Person{id='3', name='張三', address='河南'}
Person{id='4', name='張三', address='河南'}
Person{id='5', name='張三', address='河南'}
Person{id='6', name='張三', address='河南'}
Person{id='7', name='張三', address='河南'}
Person{id='8', name='張三', address='河南'}
Person{id='9', name='張三', address='河南'}
Person{id='10', name='張三', address='河南'}
(1)實(shí)體類(private String id)
public class Person{
private String id;
private String name;
private String address;
public Person(String id, String name, String address) {
this.id = id;
this.name = name;
this.address = address;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "Person{" +
"id='" + id + '\'' +
", name='" + name + '\'' +
", address='" + address + '\'' +
'}';
}
}
(2)測試類
public class ArrayListTest {
public static void main(String[] args) {
List<Person> list=Lists.newArrayList();
//產(chǎn)生10以內(nèi)的隨機(jī)數(shù)
int num = (int)(Math.random()*100+1);
for(int i=num;i>0;i--){
list.add(new Person(""+i,"張三","河南"));
}
for(Object o : list){
System.out.println(o);
}
System.out.println("++++++++++++++++++++++++++++++++++++");
Collections.sort(list, new Comparator<Person>() {
@Override
public int compare(Person o1, Person o2) {
return new Double(o1.getId()).compareTo(new Double(o2.getId()));
}
});
for(Object o : list){
System.out.println(o);
}
}
}
(3)結(jié)果
Person{id='10', name='張三', address='河南'}
Person{id='9', name='張三', address='河南'}
Person{id='8', name='張三', address='河南'}
Person{id='7', name='張三', address='河南'}
Person{id='6', name='張三', address='河南'}
Person{id='5', name='張三', address='河南'}
Person{id='4', name='張三', address='河南'}
Person{id='3', name='張三', address='河南'}
Person{id='2', name='張三', address='河南'}
Person{id='1', name='張三', address='河南'}
++++++++++++++++++++++++++++++++++++
Person{id='1', name='張三', address='河南'}
Person{id='2', name='張三', address='河南'}
Person{id='3', name='張三', address='河南'}
Person{id='4', name='張三', address='河南'}
Person{id='5', name='張三', address='河南'}
Person{id='6', name='張三', address='河南'}
Person{id='7', name='張三', address='河南'}
Person{id='8', name='張三', address='河南'}
Person{id='9', name='張三', address='河南'}
Person{id='10', name='張三', address='河南'}
另外一種稱為自然排序,參與排序的對象需實(shí)現(xiàn)comparable接口,重寫其compareTo()方法,方法體中實(shí)現(xiàn)對象的比較大小規(guī)則。
(1)實(shí)體類
public class Person implements Comparable{
private String id;
private String name;
private String address;
public Person(String id, String name, String address) {
this.id = id;
this.name = name;
this.address = address;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "Person{" +
"id='" + id + '\'' +
", name='" + name + '\'' +
", address='" + address + '\'' +
'}';
}
@Override
public int compareTo(Object o) {
if (o instanceof Person){
Person o1 = (Person)o;
return new Double(this.getId()).compareTo(new Double(o1.getId()));
}
throw new ClassCastException("不能轉(zhuǎn)換為Person類型的對象...");
}
}
(2)測試類
public class ArrayListTest {
public static void main(String[] args) {
List<Person> list=Lists.newArrayList();
//產(chǎn)生10以內(nèi)的隨機(jī)數(shù)
int num = (int)(Math.random()*100+1);
for(int i=num;i>0;i--){
list.add(new Person(""+i,"張三","河南"));
}
for(Object o : list){
System.out.println(o);
}
System.out.println("++++++++++++++++++++++++++++++++++++");
Collections.sort(list);
for(Object o : list){
System.out.println(o);
}
}
}
(3)結(jié)果
Person{id='10', name='張三', address='河南'}
Person{id='9', name='張三', address='河南'}
Person{id='8', name='張三', address='河南'}
Person{id='7', name='張三', address='河南'}
Person{id='6', name='張三', address='河南'}
Person{id='5', name='張三', address='河南'}
Person{id='4', name='張三', address='河南'}
Person{id='3', name='張三', address='河南'}
Person{id='2', name='張三', address='河南'}
Person{id='1', name='張三', address='河南'}
++++++++++++++++++++++++++++++++++++
Person{id='1', name='張三', address='河南'}
Person{id='2', name='張三', address='河南'}
Person{id='3', name='張三', address='河南'}
Person{id='4', name='張三', address='河南'}
Person{id='5', name='張三', address='河南'}
Person{id='6', name='張三', address='河南'}
Person{id='7', name='張三', address='河南'}
Person{id='8', name='張三', address='河南'}
Person{id='9', name='張三', address='河南'}
Person{id='10', name='張三', address='河南'}
以上就是動(dòng)力節(jié)點(diǎn)小編介紹的"Java中的各種集合排序"的內(nèi)容，希望對大家有幫助，如有疑問，請?jiān)诰€咨詢，有專業(yè)老師隨時(shí)為您服務(wù)。
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