本文实例为大家分享了java实现页面置换算法的具体代码，供大家参考，具体内容如下

原理就不说了，直接上代码

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", "2", "1", "2", "3", "5", "2", "3", "7", "6"};

// 内存块

int memory = 3;

List list = new ArrayList<>();

for(int i = 0; i < inputStr.length; i++){

if(i == 0){

list.add(inputStr[i]);

System.out.println("第"+ i +"次访问：\t\t" + ListUtils.listToString(list));

}else {

if(ListUtils.find(list, inputStr[i])){

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

}

}

}

}

}

LRU

import utils.ListUtils;

import java.util.ArrayList;

import java.util.List;

/**

* 最近最久未用置换算法

* @author cnkeysky

*

*/

public class LRU {

public static void main(String[] args) {

String[] inputStr = {"6", "7", "6", "5", "9", "6", "8", "9", "7", "6", "9", "6"};

// 内存块

int memory = 3;

List list = new ArrayList<>();

for(int i = 0; i < inputStr.length; i++){

if(i == 0){

list.add(inputStr[i]);

System.out.println("第"+ i +"次访问：\t\t" + ListUtils.listToString(list));

}else {

if(ListUtils.find(list, inputStr[i])){

// 存在字符串，则获取该下标

int index = ListUtils.findIndex(list, inputStr[i]);

// 下标不位于栈顶时，且list大小不为1时

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" + "访问：\t\t" + ListUtils.listToString(list));

}else{

if(list.size()>= memory) {

list.remove(0);

list.add(inputStr[i]);

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

}else {

list.add(inputStr[i]);

System.out.println("第" + i + "次" + "访问：\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", "7", "6", "5", "9", "6", "8", "9", "7", "6", "9", "6"};

List list = new ArrayList<>();

// 内存块

int memory = 3;

// 缺页次数

int count = 0;

String[] clock = new String[memory];

int indexNext = 0;

int index = 0;

// 初始化时钟

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 +"次访问：\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 +"次访问：\t\t" + ListUtils.listToString(list));

}else {

if(list.size() < memory) {

list.add(inputStr[i]);

clock[indexNext] = "1";

indexNext++;

System.out.println("第"+ i +"次访问：\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 +"次访问：\t\t" + ListUtils.listToString(list));

}

}

}

if(indexNext > memory - 1) {

indexNext = Math.abs(memory - indexNext);

}

}

System.out.println("缺页次数：" + (inputStr.length-count));

}

}

工具类ListUtils

import java.util.List;

public class ListUtils {

public ListUtils() {

}

/**

* 输出

* @param list 将List转为数组并输出, 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中查找是否有str

* @param list

* @param str

* @return

*/

public static boolean find(List list, String str){

boolean flag = false;

for(String lis : list){

if(lis.equals(str)){

flag = true;

}

}

return flag;

}

/**

* 在List中查找是否有String,如果有返回下标, 否则返回 -1

* @param list

* @param str

* @return

*/

public static int findIndex(List 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 下标

* @param clock 时钟

* @param range 当前使用内存块

* @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;

}

/**

* 在数组中查找是否存在该字符串

* @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;

}

/**

* 获取二维数组中同一列的行的长度

* @param str 数据

* @param length 二维数组的列

* @param memory 内存块

* @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;

}

}

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时间： 2020-08-09