Sample Java code for sorting ArrayList
- 2020-04-01 04:24:01
- OfStack
No more crap, just post the code.
class term {
String str;
int id;
public term(String str, int id) {
this.str = str;
this.id = id;
}
public String toString() {
return str+" "+id;
}
}
class sterm implements Comparable{
String str;
int id;
public sterm(String str, int id) {
this.str = str;
this.id = id;
}
public int compareTo(Object o) {
return ((sterm)o).id - id;
}
public String toString() {
return str+" "+id;
}
}
//method1: explicit implements Comparator
class termComparator implements Comparator {
public int compare (Object o1, Object o2) {
return ((term)o1).id - ((term)o2).id;
}
}
public class t1 {
public static void main(String[] args) {
// TODO Auto-generated method stub
// ArrayList<Integer> arr = new ArrayList<Integer>( Arrays.asList(3,1,3,7,8,0));
//
// Collections.sort(arr, new Comparator(){
//
// public int compare(Object o1, Object o2){
// return new Double((Integer)o1).compareTo(new Double ((Integer)o2));
// }
// });
//method1
List<term> ls = new ArrayList<term>();
ls.add(new term("a",1));
ls.add(new term("b",5));
ls.add(new term("c",2));
ls.add(new term("d",2));
ls.add(new term("e",3));
ls.add(new term("f",0));
Collections.sort(ls, new termComparator());
System.out.println(ls);//[f 0, a 1, c 2, d 2, e 3, b 5]
//method2: anonymous implements
Collections.sort(ls, new Comparator(){
public int compare(Object o1, Object o2){
return ((term)o2).id - ((term)o1).id;
}
});
System.out.println(ls);//[b 5, e 3, c 2, d 2, a 1, f 0]
//method3:instantiate a Comparator template
Comparator<term> termCmp = new Comparator<term>() {
public int compare(term t1, term t2) {
return t1.id - t2.id;
}
};
Collections.sort(ls, termCmp);
System.out.println(ls);//[f 0, a 1, c 2, d 2, e 3, b 5]
//method4:element implements Comparable
List<sterm> lss = new ArrayList<sterm>();
lss.add(new sterm("a",1));
lss.add(new sterm("b",5));
lss.add(new sterm("c",2));
lss.add(new sterm("d",2));
lss.add(new sterm("e",3));
lss.add(new sterm("f",0));
Collections.sort(lss);
System.out.println(lss);//[b 5, e 3, c 2, d 2, a 1, f 0]
}
}
Prioritizing yqueue is used in a similar way to prioritizing the above, there are three ways:
class WordFreq implements Comparable{
public String wd;
public int freq;
public WordFreq(String wd, int freq) {
this.wd = wd;
this.freq = freq;
}
public int compareTo(Object o) {
return ((WordFreq)o).freq - freq;
}
public String toString() {
return wd+" "+freq;
}
}
public class testt {
public static void main(String[] args) {
// TODO Auto-generated method stub
PriorityQueue<WordFreq> pq = new PriorityQueue<WordFreq>();
pq.offer(new WordFreq("aaa", 3));
pq.offer(new WordFreq("bbb", 4));
pq.offer(new WordFreq("ccc",1));
while(pq.peek() != null) {
System.out.println(pq.poll());
}//Output from large to small
}
}
Pay attention to,
for (WordFreq wf : pq) {
System.out.println(wf);
}
Traversal order is not guaranteed
If List< String> For ls to sort, you don't need to write Comparator, because String itself has an implementation of compareTo.