problem
实验内容：
编写一个请求页式存储管理模拟程序，通过对页面置换过程的模拟，加深对请求页式存储管理方式基本原理及实现过程的理解。
要求：
-
从键盘输入页面访问序列及分配给进程的内存块数；
-
分别采用OPT、FIFO和LRU算法进行页面置换（说明：对于OPT算法，在有多个页面可选的情况下，先淘汰较早进入的页面）。
-
计算缺页次数及缺页率。
测试用例格式如下：
输入：
算法（1--OPT，2--FIFO，3--LRU）
内存块数
页面序列（页面1,页面2,页面3,...)
输出：
页面变化时内存块装入页面列表1-是否命中/页面变化时内存块装入页面列表2-是否命中/...
缺页次数
其中：
页面变化时内存块装入页面列表：内存块1装入页面,内存块2装入页面,内存块3装入页面...，未装入任何页面时由"-”表示
是否命中：1-命中，0-缺页
测试用例
| 测试输入 | 期待的输出 |
|---|---|
| 1 3 1,2,3,4,1,2,5,1,2,3,4,5 |
1,-,-,0/1,2,-,0/1,2,3,0/1,2,4,0/1,2,4,1/1,2,4,1/1,2,5,0/1,2,5,1/1,2,5,1/3,2,5,0/3,4,5,0/3,4,5,1 7 |
ac code
import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;
import java.util.Scanner;
class Page {
private boolean isEmpty;
private int id;
private String idx;
private int next = Integer.MAX_VALUE;
public Page(boolean isEmpty, int id, String idx) {
this.isEmpty = isEmpty;
this.id = id;
this.idx = idx;
}
public int getNext() {
return next;
}
public void setNext(int next) {
this.next = next;
}
public boolean isEmpty() {
return isEmpty;
}
public void setEmpty(boolean empty) {
isEmpty = empty;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getIdx() {
return idx;
}
public void setIdx(String idx) {
this.idx = idx;
}
@Override
public String toString() {
if (isEmpty) {
return "-";
}
return idx;
}
}
class Memory {
private List<Page> memory = new LinkedList<>();
private int block;
private int count;
private int lruFirst;
private int id = 0;
Memory(int block) {
this.block = block;
for (int i = 0 ;i < block ; i++){
this.memory.add(new Page(true,0,"-"));
}
}
public boolean isFull(){
return this.count == this.block;
}
public int getCount() {
return count;
}
public void print(int get){
String res = this.toString();
System.out.print(res + String.valueOf(get));
}
public boolean contains(String val) {
for (Page p : memory) {
if (p.getIdx().equals(val)) {
return true;
}
}
return false;
}
public void add(String val) {
count += 1;
for (Page s : memory) {
if (s.isEmpty()){
s.setIdx(val);
s.setId(id++);
s.setEmpty(false);
break;
}
}
}
public void fifo(String val) {
Page first = memory.get(0);
int min = Integer.MAX_VALUE;
for (Page p : memory) {
if (p.getId() < min) {
min = p.getId();
first = p;
}
}
first.setId(id++);
first.setIdx(val);
first.setEmpty(false);
}
public void opt(String val) {
Page first = memory.get(0);
int max = Integer.MIN_VALUE;
boolean wq = false;
for (Page p : memory) {
if (p.getNext() > max) {
max = p.getNext();
first = p;
if (p.getNext() == Integer.MAX_VALUE){
wq= true;
break;
}
}
}
if (wq) {
int mid = Integer.MAX_VALUE;
for (Page p : memory) {
if (p.getNext()==Integer.MAX_VALUE) {
if (p.getId() < mid) {
mid = p.getId();
first = p;
}
}
}
}
first.setId(id++);
first.setIdx(val);
first.setEmpty(false);
}
public void searchNxt(List<String> pages,int start) {
for (Page p : memory){
p.setNext(Integer.MAX_VALUE);
}
for (Page p : memory) {
for (int i = start + 1; i < pages.size(); i++) {
if (pages.get(i).equals(p.getIdx())) {
p.setNext(i);
break;
}
}
}
}
public void lru(String val) {
memory.remove(0);
memory.add(new Page(false,id++,val));
}
public void toLast(String val) {
for (Page page: memory) {
if (page.getIdx().equals(val)) {
memory.remove(page);
memory.add(count-1,page);
break;
}
}
}
@Override
public String toString() {
StringBuffer res = new StringBuffer();
for (Page ech : memory) {
res.append(ech.toString() + ",");
}
return res.toString();
}
}
public class Main {
private static int method;
private static int block;
private static int miss = 0;
private static List<String> pages;
private static Memory memory ;
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
method = scanner.nextInt();
block = scanner.nextInt();
memory = new Memory(block);
scanner.nextLine();
pages = Arrays.asList(scanner.nextLine().split(","));
switch (method) {
case 1:
opt();
break;
case 2:
fifo();
break;
case 3:
lru();
break;
}
}
private static void fifo(){
for (int i = 0 ; i < pages.size() ; i++) {
String val = pages.get(i);
if (memory.contains(val)){
memory.print(1);
}else if (!memory.isFull()){
miss += 1;
memory.add(val);
memory.print(0);
} else {
memory.fifo(val);
memory.print(0);
miss += 1;
}
if (i == pages.size() -1) {
System.out.println();
}else {
System.out.print("/");
}
}
System.out.println(miss);
}
private static void opt(){
for (int i = 0 ; i < pages.size() ; i++) {
String val = pages.get(i);
if (memory.contains(val)){
memory.print(1);
}else if (!memory.isFull()){
miss += 1;
memory.add(val);
memory.print(0);
}else {
memory.searchNxt(pages,i);
memory.opt(val);
memory.print(0);
miss += 1;
}
if (i == pages.size() -1) {
System.out.println();
}else {
System.out.print("/");
}
}
System.out.println(miss);
}
private static void lru(){
for (int i = 0 ; i < pages.size() ; i++) {
String val = pages.get(i);
if (memory.contains(val)){
memory.toLast(val);
memory.print(1);
}else if (!memory.isFull()){
memory.add(val);
memory.print(0);
miss += 1;
} else {
memory.lru(val);
memory.print(0);
miss += 1;
}
if (i == pages.size() -1) {
System.out.println();
}else {
System.out.print("/");
}
}
System.out.println(miss);
}
}
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