java實現頁面置換演算法

阿新 • • 發佈：2020-08-10

本文例項為大家分享了java實現頁面置換演算法的具體程式碼，供大家參考，具體內容如下

原理就不說了，直接上程式碼

FIFO

import java.util.ArrayList;
import java.util.List;

import utils.ListUtils;


/**
 * 
 * 
 * @author cnkeysky
 *
 */

public class FIFO {

 public void run() {
 String[] inputStr = {"1","2","3","4","1","5","7","6"};
 // 記憶體塊
 int memory = 3;
 List<String> list = new ArrayList<>();
 for(int i = 0; i < inputStr.length; i++){
  if(i == 0){
  list.add(inputStr[i]);
  System.out.println("第"+ i +"次訪問：\t\t" + ListUtils.listToString(list));
  }else {
  if(ListUtils.find(list,inputStr[i])){
   System.out.println("第" + i + "次" + "訪問：\t\t" + ListUtils.listToString(list));
  }else{
   if(list.size() < memory){
   list.add(inputStr[i]);
   }else{
   list.remove(0);
   list.add(inputStr[i]);

   }
   System.out.println("第" + i + "次" + "訪問：\t\t" + ListUtils.listToString(list));
  }
  }
 }
 }

}

LRU

import utils.ListUtils;

import java.util.ArrayList;
import java.util.List;

/**
 * 最近最久未用置換演算法
 * @author cnkeysky
 *
 */

public class LRU {

 public static void main(String[] args) {
 String[] inputStr = {"6","6","9","8",inputStr[i])){
   // 存在字串，則獲取該下標
   int index = ListUtils.findIndex(list,inputStr[i]);
   // 下標不位於棧頂時，且list大小不為1時
   if(!(list.get(list.size() - 1)).equals(inputStr[i]) && list.size() != 1) {
   String str = list.get(index);
   list.remove(index);
   list.add(str);
   }
   System.out.println("第" + i + "次" + "訪問：\t\t" + ListUtils.listToString(list));
  }else{
   if(list.size()>= memory) {
   list.remove(0);
   list.add(inputStr[i]);
   System.out.println("第" + i + "次" + "訪問：\t\t" + ListUtils.listToString(list));
   }else {
   list.add(inputStr[i]);
   System.out.println("第" + i + "次" + "訪問：\t\t" + ListUtils.listToString(list));
   }
  }
  }
 }
 }
}

Clock

import java.util.ArrayList;
import java.util.List;

import utils.ListUtils;

/**
 * 
 * 
 * @author cnkeysky
 *
 */
public class Clock {

 public static void main(String[] args) {
 String[] inputStr = {"6","6"};
 List<String> list = new ArrayList<>();
 // 記憶體塊
 int memory = 3;
 // 缺頁次數
 int count = 0;
 String[] clock = new String[memory];
 int indexNext = 0;
 int index = 0;
 // 初始化時鐘
 for(int i = 0; i < memory; i++) {
  clock[i] = "0";
 }
 for(int i = 0; i < inputStr.length; i++) {
  int indexPre = 0;
  if (i == 0) {
  list.add(inputStr[i]);
  clock[indexNext] = "1";
  indexNext++;
  System.out.println("第"+ i +"次訪問：\t\t" + ListUtils.listToString(list));
  }else {

  if(ListUtils.find(list,inputStr[i])) {
   indexPre = ListUtils.findIndex(list,inputStr[i]);
   if(clock[indexPre].equals("0")) {
   clock[indexPre] = "1";
   }
   count++;
   System.out.println("第"+ i +"次訪問：\t\t" + ListUtils.listToString(list));
  }else {
   if(list.size() < memory) {
   list.add(inputStr[i]);
   clock[indexNext] = "1";
   indexNext++;
   System.out.println("第"+ i +"次訪問：\t\t" + ListUtils.listToString(list));
   }else {
   index = ListUtils.findZero(indexNext,clock,memory);
   list.remove(index);
   list.add(index,inputStr[i]);
   clock[index] = "1";
   indexNext = index + 1;
   System.out.println("第"+ i +"次訪問：\t\t" + ListUtils.listToString(list));
   }
  }
  }
  if(indexNext > memory - 1) {
  indexNext = Math.abs(memory - indexNext);
  }
 }
 System.out.println("缺頁次數：" + (inputStr.length-count));
 }

}

工具類ListUtils

import java.util.List;

public class ListUtils {

 public ListUtils() {

 }

 /**
 * 輸出
 * @param list 將List轉為陣列並輸出,out: 2,3,4 
 * @return
 */
 public static String listToString(List list){

 StringBuffer content = new StringBuffer();
 for(int i = 0; i < list.size(); i++){
  content.append(list.get(i));
  if(i < list.size() - 1){
  content.append(",");
  }
 }
 return content.toString();
 }

 /**
 * 在list中查詢是否有str
 * @param list
 * @param str
 * @return
 */
 public static boolean find(List<String> list,String str){
 boolean flag = false;
 for(String lis : list){
  if(lis.equals(str)){
  flag = true;
  }
 }
 return flag;
 }

 /**
 * 在List中查詢是否有String,如果有返回下標,否則返回 -1
 * @param list
 * @param str
 * @return
 */
 public static int findIndex(List<String> list,String str) {

 int index = 0;
 for(String lis : list) {
  if(lis.equals(str)) {
  return index;
  }
  index++;
 }
 return -1;
 }

 public static boolean clockJudge(String[] clock,int index) {
 if(clock[index].equals("0")) {
  return true;
 }
 return false;
 }
 /**
 * 
 * @param index 下標
 * @param clock 時鐘
 * @param range 當前使用記憶體塊
 * @return
 */
 public static int findZero(int index,String[] clock,int range) {

 while(true) {

  if(clock[index].equals("0")) {
  break;
  }else {
  clock[index] = "0";
  index++;
  if(index > range-1) {
   index = Math.abs(range - index);
  }
  }
 }
 return index;
 }

 /**
 * 在陣列中查詢是否存在該字串
 * @param obj
 * @param str
 * @return
 */
 public static boolean strJudge(Object[] obj,String str) {
 boolean flag = false;
 if(obj == null) {
  return flag;
 }
 for(int i = 0; i < obj.length; i++) {
  if(str.equals(obj[i])) {
  flag = true;
  break;
  }
 }
 return flag;
 }

 /**
 * 獲取二維陣列中同一列的行的長度
 * @param str 資料
 * @param length 二維陣列的列
 * @param memory 記憶體塊
 * @return
 * 
 */

 public static int findNull(Object[][] str,int length,int memory) {

 int index = 0;
 if(str == null) {
  return -1;
 }
 for(int i = 0; i < memory; i++) {
  if(str[i][length] != null) {
  index = i;
  }
 }
 return index;
 }
}

以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支援我們。