Note: the note is about the implementation of page replacement algorithm by fengsigaoju boss( (35 messages) java implements the page replacement algorithm (OPT,FIFO,LRU) _fengsigaoju's blog - CSDN blog _pagereplacement algorithm code java )Learning, invasion and deletion.
I have been learning JAVA for one month. If there are any deficiencies, please point out.
First code:
import java.io.BufferedInputStream;
import java.util.*;
public class Main {
private int n;//Inner page storage box
private int m;//Number of visits
private int F;//The number of times that cannot be found directly, (F/m) is the page missing rate
private List<Integer>list=null;//Access address trend
private Map<Integer,Integer>map=null;
public Main(){
F=0;
map=new HashMap<Integer,Integer>();//Store the contents of each internal storage page box
Scanner cin=new Scanner(new BufferedInputStream(System.in));
System.out.println("Please enter the user access page address");
list=new ArrayList<Integer>();
String s=cin.nextLine();
String []s1=s.split(" ");
m=s1.length;
for (int i=0;i<m;i++)
list.add(Integer.valueOf(s1[i]));
System.out.println("Please enter the number of inner leaf boxes");
n=cin.nextInt();
menu();
switch(cin.nextInt()){
case 1:OPT();break;
case 2:FIFO();break;
case 3:LRU();break;
case 4:LFU();break;
}
cin.close();
}
public void menu(){
System.out.println("**** To select the best replacement algorithm, press 1 **********");
System.out.println("**** To select a FIFO replacement algorithm, press 2 *******");
System.out.println("**** To select the nearest and farthest unused replacement algorithm, press 3 ***");
System.out.println("**** use lfr Press 4 ******************");
}
public void OPT(){//Optimal permutation algorithm
int j;
for (int i=0;i<m;i++)
{
int k=list.get(i);//Pending element
//System.out.print(map);
if (!map.containsValue(k)){
F++;//Cannot directly find times plus 1
if (map.size()<n){//If it's not full
int temp=map.size();
map.put(temp, k);
}
else{//If it's full
int index=0;//Which position will be eliminated
int min=0;//Initial maximum length
for (int t=0;t<n;t++)
{
for (j=i+1;j<m;j++){//See which one appears last
if (list.get(j)==map.get(t)){//Found for the first time
if (j-i>min){
index=t;//Update value
min=j-i;
}
break;
}
}
if (j==m){//If in the end
index=t;
min=j-i;
}
}
map.remove(index);
map.put(index,k);//Modify table elements
}
}
}
System.out.println("The bit error rate is:"+F*1.0/m);
}
public void FIFO(){//FIFO replacement algorithm
Queue<Integer>q=new LinkedList<Integer>();
for (int i=0;i<m;i++)
{
int k=list.get(i);//Pending element
if (!map.containsValue(k)){
F++;//Cannot directly find times plus 1
if (map.size()<n){//If it's not full
int temp=map.size();
map.put(temp, k);
q.offer(temp);
}
else
{
int temp=q.poll();//Excluded element location
map.remove(temp);
map.put(temp,k);
q.offer(temp);
}
}
}
System.out.println("The bit error rate is:"+F*1.0/m);
}
public void LRU(){//Most recently, no permutation algorithm has been used
List<Integer>linkedlist=new LinkedList<Integer>();
int start=0;
for (int i=0;i<m;i++)
{
int k=list.get(i);//Pending element
if (!map.containsKey(k)){
F++;//Cannot directly find times plus 1
if (map.size()<n){//If it's not full
int temp=map.size();
map.put(k,temp);
linkedlist.add(k);//Add location
}
else
{
int temp=linkedlist.get(0);
int c=map.get(temp);//position
map.remove(temp);
map.put(k,c);
linkedlist.remove(0);
linkedlist.add(k);
}
}
else//If you include this value, take it away and press it in later
{
int d=linkedlist.indexOf(k);//Find existing location
linkedlist.remove(d);
linkedlist.add(k);
}
}
System.out.println("The bit error rate is:"+F*1.0/m);
}
public void LFU() {
for (int i=0;i<m;i++)
{
int k=list.get(i);//Pending element
if (!map.containsValue(k)){
F++;
if (map.size()<n){
int temp=map.size();
map.put(temp, k);
}
else{
int index=0;
int min=0;
int num=0;
for (int t=0;t<n;t++)
{
for (int j=i-1;j>0;j--){
if (list.get(j)==map.get(t)){
num++;
}
if(min<num){
min=num;
index=t;
}
}
}
map.remove(index);
map.put(index,k);
}
}
}
System.out.println("The bit error rate is:"+F*1.0/m);
}
public static void main(String args[]){
Main p=new Main();
}
}The fourth method I added myself is not particularly good, but it meets the requirements of the textbook.
Next is the understanding of this Code:
1, Code used:
1. The import BufferedInputStream in the first line is a little deeper for beginners. When this line arrives, the original
Scanner cin=new Scanner(new BufferedInputStream(System.in));
Change to
Scanner cin=new Scanner(System.in);
It can also operate normally;
2.List
List <integer> list=new ArrayList<Integer>();
This code allows us to call the built-in functions in the List interface, such as add and get.
3.HashMap
Hash table is a very practical type. Its main feature is that it has key value pairs. From this point alone, it is easy to contact the dictionary in Python, but it has far more functions than it.
Many built-in functions can be judged literally:
containsValue(k) finds whether there is a value of K in the table.
size() returns the number of key value pairs.
put() adds or modifies key value pairs.
remove() moves out the key value pair, and the return value is the deleted value.
get() returns the value corresponding to the key.
4.Queue
q.offer: there are two adding methods in the queue, add and offer. The difference between the two is that add will report an error when the queue is full, and offer will return false, while I haven't found other differences yet.
q.remove: like pop, it deletes the header element. When the queue is empty, remove reports an error and pop returns null.
5.linkedlist
Linked list is a very common type. I won't repeat it here.
2, Problems encountered reading code
1. When reading LRU (), the temp pointer made me dizzy... Later, the compiler found that the temps in the two if are not the same at all... This shows the importance of the compiler
3, Summary
Generally speaking, it is still relatively basic code. School experiments are really difficult. Write notes in this regard to find inspiration. I wanted to write a longer result. My girlfriend asked me to write it for her..
This is the notes of chicken and vegetable that I have studied for a month. If there are mistakes, please correct them.