P1059

package Package;

import java.io.*;
import java.util.*;


public class Main {

	public static void main(String[] args) throws IOException {
		
		StreamTokenizer in = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
		PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
		
		in.nextToken();
		int N = (int)in.nval;
		
		HashSet<Integer> hs=new HashSet<Integer>();
		
		for(int i=0; i<N; i++) {
			in.nextToken();
			hs.add((int)in.nval);
		}
		
		ArrayList<Integer> al=new ArrayList<Integer>();
		al.addAll(hs);
		Collections.sort(al);
		
		out.print(al.size()+"\n");
		
		Iterator<Integer> it = al.iterator();

		while(it.hasNext()) {
		    out.print(it.next()+" ");
		}
		
		out.flush();
		out.close();
	}
}

一、创建HashSet对象并添加元素，目的：去重

创建对象：

HashSet<Integer> hs=new HashSet<Integer>();

添加元素：

hs.add((int)in.nval);

二、创建ArrayList对象并添加元素，目的：排序

创建对象：

ArrayList<Integer> al=new ArrayList<Integer>();

将HashSet对象转化为ArrayList对象元素：

al.addAll(hs);

三、创建Iterator对象并迭代输出

创建对象：

Iterator<Integer> it = al.iterator();

循环输出元素：

while(it.hasNext()) {
		    out.print(it.next()+" ");
		}

四、直接用TreeSet

package Package;

import java.io.*;
import java.util.*;


public class Main {

	public static void main(String[] args) throws IOException {
		
		StreamTokenizer in = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
		PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
		
		in.nextToken();
		int N = (int)in.nval;
		
		TreeSet<Integer> ts=new TreeSet<Integer>();
		
		for(int i=0; i<N; i++) {
			in.nextToken();
			ts.add((int)in.nval);
		}
	
		
		out.print(ts.size()+"\n");
		
		Iterator<Integer> it = ts.iterator();

		while(it.hasNext()) {
		    out.print(it.next()+" ");
		}
		
		out.flush();
		out.close();
	}
}