学习了Comparator,接着看Collection
先看一个问题正序输出几个字母
package iterator;
import java.util.Comparator;
import java.util.Iterator;
import java.util.TreeSet;
/**
* @Auther: Xinbai
* @Date:2020/5/19 20:39
*/
public class TreeSetTest3 {
public static void main(String[] args) {
TreeSet set = new TreeSet();
set.add("C");
set.add("A");
set.add("B");
set.add("E");
set.add("F");
set.add("D");
for (Iterator iter = set.iterator(); iter.hasNext(); ) {
String value = (String)iter.next();
System.out.println(value);
}
}
}
那么反序?
package iterator;
import java.util.Comparator;
import java.util.Iterator;
import java.util.TreeSet;
/**
* @Auther: Xinbai
* @Date:2020/5/19 20:39
*/
public class TreeSetTest3 {
public static void main(String[] args) {
TreeSet set = new TreeSet(new Tess());
set.add("C");
set.add("A");
set.add("B");
set.add("E");
set.add("F");
set.add("D");
for (Iterator iter = set.iterator(); iter.hasNext(); ) {
String value = (String)iter.next();
System.out.println(value);
}
}
}
class Tess implements Comparator{
@Override
public int compare(Object o1, Object o2) {
String s1=(String)o1;
String s2=(String)o2;
return s2.compareTo(s1);
}
}
package Collections;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.LinkedList;
/**
* @Auther: Xinbai
* @Date:2020/5/21 8:49
*/
public class CollectionsTest {
public static void main(String[] args) {
LinkedList list=new LinkedList();
list.add(new Integer(-8));
list.add(new Integer(20));
list.add(new Integer(-20));
list.add(new Integer(8));
Comparator r= Collections.reverseOrder();
Collections.sort(list,r);
for (Iterator iter=list.iterator(); iter.hasNext();){
System.out.println(iter.next());
}
}
那么我们再看Collections的一个属性shuffle【这个属性使得数是随机出现,也是捣乱顺序】
Collections.shuffle(list);
for (Iterator iter=list.iterator(); iter.hasNext();){
System.out.println(iter.next());
}
最小值和最大值:
System.out.println(Collections.min(list));
System.out.println(Collections.max(list));
输出结果:
-20
20