Java class 的排序
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import java.util.*;
class Node implements Comparable
{
int x,y;
public int compareTo(Object obj){
Node oo=(Node)obj;
if(oo.x < this.x || oo.x == this.x && oo.y <this.y)return 1;
return -1;
}
}
public class Main {
public static void main(String[] args) throws Exception {
Scanner cin = new Scanner(System.in);
Node a[]=new Node[11];
int i,j,k,l;
for(i=1;i<=10;i++) {
a[i]=new Node();
a[i].x=Math.abs(5-i); a[i].y=10-Math.abs(7-i);
}
Arrays.sort(a, 1, 11);
for(i=1;i<=10;i++)System.out.println(a[i].x+" "+a[i].y);
}
}
Java Vector 的使用
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import java.util.*;
public class Main {
public static void main(String[] args) throws Exception {
Scanner cin = new Scanner(System.in);
Vector V=new Vector();
V.add(1); V.add(1.234); V.add('a'); V.add("abcd");
System.out.println((Integer)V.get(0));
System.out.println((Double)V.get(1));
System.out.println((Character)V.get(2));
System.out.println((String)V.get(3));
}
}
Java 队列的使用
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import java.util.*;
public class Main {
public static void main(String[] args) throws Exception {
Scanner cin = new Scanner(System.in);
Queue Q=new LinkedList<Integer>();
int i,j,k,l;
while(!Q.isEmpty())Q.poll(); // 清空队列
for(i=1;i<=10;i++)Q.offer(i);
for(i=1;i<=10;i++){
k=(Integer)Q.poll();
System.out.println(k);
}
}
}
Java 优先队列的使用
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import java.util.*;
public class Main {
public static void main(String[] args) throws Exception {
Scanner cin = new Scanner(System.in);
PriorityQueue<Integer> Q = new PriorityQueue<Integer>(30,
new Comparator<Integer>(){
public int compare(Integer aa, Integer bb) {
if(aa < bb)return 1;
return -1;
}
});
int i,j,k,l;
Q.clear();
for(i=1;i<=10;i++)Q.offer(i);
while(!Q.isEmpty()) {
k=(Integer)Q.poll();
System.out.println(k);
}
}
}
http://www.yiibai.com/java/util/java_util_hashset.html
Java Collection 的使用
boolean contains(Object o) 如果此set包含指定的元素，此方法返回true。
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import java.util.*;
public class Main {
public static void main(String[] args) throws Exception {
Scanner cin = new Scanner(System.in);
Collection set=new HashSet();
Collection set1=new ArrayList();
Collection set2=new LinkedList();
ArrayList LI=new ArrayList();
LinkedList LD=new LinkedList();
int i,j,k,l;
set.clear(); // set1 set2 LI LD 用法类似
set.add(1); set.add(1.234); set.add('a'); set.add("abcd");
System.out.println(set.toString());
set.remove(1); set.remove(3);
System.out.println(set.toString());
}
}
http://www.yiibai.com/java/util/java_util_hashmap.html
Java HashMap（很好用） TreeMap
boolean containsKey(Object key) 如果此映射包含指定键的映射此方法返回true。
boolean containsValue(Object value) 如果此映射一个或多个键映射到指定值，该方法返回true
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import java.util.*;
public class Main {
public static void main(String[] args) throws Exception {
Scanner cin = new Scanner(System.in);
Map map=new HashMap();
int i,j,k,l;
map.clear();
for(i=1;i<=10;i++)map.put(Math.pow(10,i), i);
for(i=1;i<=10;i++)System.out.println((Integer)map.get(Math.pow(10,i)));
System.out.println();
Map tree=new TreeMap();
tree.clear();
for(i=1;i<=10;i++)tree.put(i,10-i);
for(i=1;i<=10;i++)
{
k=(Integer)tree.get(i);
System.out.println(k);
}
}
}
