java实现LFU算法
时间: 2023-08-29 08:10:41 浏览: 69
C知道: 要在 Java 中实现 LFU (Least Frequently Used) 算法,您可以按照以下步骤进行操作:
1. 创建一个类来表示缓存项,其中包含键、值和使用计数等属性。
2. 创建一个类来表示 LFU 缓存,其中包含一个哈希表用于快速查找缓存项,以及一个双向链表用于按使用频率排序缓存项。
3. 在 LFU 缓存类中实现以下方法:
- `get(key)`:根据键获取缓存项的值,并将该项的使用计数加1,同时更新链表中的位置。
- `put(key, value)`:将键值对添加到缓存中,如果缓存已满,则根据 LFU 算法删除最不常使用的项。
- `evict()`:根据 LFU 算法删除最不常使用的项。
4. 在主程序中创建一个 LFU 缓存对象,并使用 `get` 和 `put` 方法来测试算法的正确性。
这只是一个简单的实现示例,具体的代码实现可能会有所不同,取决于您的需求和设计。希望这个提示能帮到您!如有更多问题,请随时提问。
相关问题
java手动实现lfu
LFU(Least Frequently Used)是一种缓存淘汰算法,可以用于对缓存中的数据进行淘汰。下面是 Java 手动实现 LFU 的示例代码:
```
import java.util.HashMap;
import java.util.LinkedHashSet;
import java.util.Map;
public class LFUCache<K, V> {
private Map<K, V> cacheMap; // 存放缓存数据
private Map<K, Integer> freqMap; // 存放缓存数据的访问频率
private Map<Integer, LinkedHashSet<K>> freqKeysMap; // 存放访问频率相同的缓存数据
private int capacity; // 缓存容量
private int minFreq; // 缓存数据的最小访问频率
public LFUCache(int capacity) {
this.cacheMap = new HashMap<>();
this.freqMap = new HashMap<>();
this.freqKeysMap = new HashMap<>();
this.capacity = capacity;
this.minFreq = 0;
}
public V get(K key) {
V value = cacheMap.get(key);
if (value == null) {
return null;
}
// 更新缓存数据的访问频率
int freq = freqMap.get(key) + 1;
freqMap.put(key, freq);
// 更新访问频率相同的缓存数据
freqKeysMap.get(freq - 1).remove(key);
if (freqKeysMap.get(freq - 1).isEmpty()) {
freqKeysMap.remove(freq - 1);
if (minFreq == freq - 1) {
minFreq++;
}
}
freqKeysMap.computeIfAbsent(freq, k -> new LinkedHashSet<>()).add(key);
return value;
}
public void put(K key, V value) {
if (capacity <= 0) {
return;
}
// 缓存数据已存在,更新其值和访问频率
if (cacheMap.containsKey(key)) {
cacheMap.put(key, value);
get(key);
return;
}
// 缓存容量已满,淘汰访问频率最小的缓存数据
if (cacheMap.size() >= capacity) {
K minFreqKey = freqKeysMap.get(minFreq).iterator().next();
freqKeysMap.get(minFreq).remove(minFreqKey);
if (freqKeysMap.get(minFreq).isEmpty()) {
freqKeysMap.remove(minFreq);
}
cacheMap.remove(minFreqKey);
freqMap.remove(minFreqKey);
}
// 添加新的缓存数据
cacheMap.put(key, value);
freqMap.put(key, 1);
freqKeysMap.computeIfAbsent(1, k -> new LinkedHashSet<>()).add(key);
minFreq = 1;
}
}
```
这个示例代码中,LFUCache 类实现了 LFU 缓存淘汰算法。在 get 方法中,缓存数据的访问频率会加 1,同时更新访问频率相同的缓存数据;在 put 方法中,如果缓存容量已满,则会淘汰访问频率最小的缓存数据,然后添加新的缓存数据。
页面置换算法java实现
以下是Java实现五种页面置换算法的示例代码:
1. Optimal算法
```java
public class Optimal {
public static void main(String[] args) {
int[] pages = {1, 3, 0, 3, 5, 6};
int[] frames = new int[3];
int faults = 0;
boolean full = false;
int farthest = 0;
int replace = 0;
for (int i = 0; i < pages.length; i++) {
int page = pages[i];
int j;
for (j = 0; j < frames.length; j++) {
if (frames[j] == page) {
break;
}
if (frames[j] == 0) {
frames[j] = page;
faults++;
full = false;
break;
}
if (j == frames.length - 1) {
full = true;
}
}
if (full) {
int[] temp = new int[frames.length];
boolean[] used = new boolean[frames.length];
for (int k = i + 1; k < pages.length; k++) {
for (int l = 0; l < frames.length; l++) {
if (pages[k] == frames[l] && !used[l]) {
temp[l] = k;
used[l] = true;
break;
}
if (l == frames.length - 1) {
temp[l] = Integer.MAX_VALUE;
}
}
}
farthest = 0;
replace = 0;
for (int k = 0; k < temp.length; k++) {
if (temp[k] > farthest) {
farthest = temp[k];
replace = k;
}
}
frames[replace] = page;
faults++;
}
System.out.print("Page " + page + ": ");
for (int k = 0; k < frames.length; k++) {
System.out.print(frames[k] + " ");
}
System.out.println();
}
System.out.println("Page faults: " + faults);
}
}
```
2. FIFO算法
```java
public class FIFO {
public static void main(String[] args) {
int[] pages = {1, 3, 0, 3, 5, 6};
int[] frames = new int[3];
int faults = 0;
int pointer = 0;
boolean full = false;
for (int i = 0; i < pages.length; i++) {
int page = pages[i];
int j;
for (j = 0; j < frames.length; j++) {
if (frames[j] == page) {
break;
}
if (frames[j] == 0) {
frames[j] = page;
faults++;
full = false;
break;
}
if (j == frames.length - 1) {
full = true;
}
}
if (full) {
frames[pointer] = page;
faults++;
pointer++;
if (pointer == frames.length) {
pointer = 0;
}
}
System.out.print("Page " + page + ": ");
for (int k = 0; k < frames.length; k++) {
System.out.print(frames[k] + " ");
}
System.out.println();
}
System.out.println("Page faults: " + faults);
}
}
```
3. LRU算法
```java
public class LRU {
public static void main(String[] args) {
int[] pages = {1, 3, 0, 3, 5, 6};
int[] frames = new int[3];
int faults = 0;
boolean full = false;
int replace = 0;
for (int i = 0; i < pages.length; i++) {
int page = pages[i];
int j;
for (j = 0; j < frames.length; j++) {
if (frames[j] == page) {
break;
}
if (frames[j] == 0) {
frames[j] = page;
faults++;
full = false;
break;
}
if (j == frames.length - 1) {
full = true;
}
}
if (full) {
int[] temp = new int[frames.length];
boolean[] used = new boolean[frames.length];
for (int k = i - 1; k >= 0; k--) {
for (int l = 0; l < frames.length; l++) {
if (pages[k] == frames[l] && !used[l]) {
temp[l] = k;
used[l] = true;
break;
}
if (l == frames.length - 1) {
temp[l] = Integer.MIN_VALUE;
}
}
}
replace = 0;
int min = temp[0];
for (int k = 1; k < temp.length; k++) {
if (temp[k] < min) {
min = temp[k];
replace = k;
}
}
frames[replace] = page;
faults++;
}
System.out.print("Page " + page + ": ");
for (int k = 0; k < frames.length; k++) {
System.out.print(frames[k] + " ");
}
System.out.println();
}
System.out.println("Page faults: " + faults);
}
}
```
4. LFU算法
```java
public class LFU {
public static void main(String[] args) {
int[] pages = {1, 3, 0, 3, 5, 6};
int[] frames = new int[3];
int[] counts = new int[3];
int faults = 0;
boolean full = false;
int replace = 0;
for (int i = 0; i < pages.length; i++) {
int page = pages[i];
int j;
for (j = 0; j < frames.length; j++) {
if (frames[j] == page) {
counts[j]++;
break;
}
if (frames[j] == 0) {
frames[j] = page;
counts[j]++;
faults++;
full = false;
break;
}
if (j == frames.length - 1) {
full = true;
}
}
if (full) {
replace = 0;
int min = counts[0];
for (int k = 1; k < counts.length; k++) {
if (counts[k] < min) {
min = counts[k];
replace = k;
}
}
frames[replace] = page;
counts[replace] = 1;
faults++;
}
System.out.print("Page " + page + ": ");
for (int k = 0; k < frames.length; k++) {
System.out.print(frames[k] + " ");
}
System.out.println();
}
System.out.println("Page faults: " + faults);
}
}
```
5. 改进型Clock算法
```java
public class Clock {
public static void main(String[] args) {
int[] pages = {1, 3, 0, 3, 5, 6};
int[] frames = new int[3];
boolean[] ref_bits = new boolean[3];
int faults = 0;
int pointer = 0;
for (int i = 0; i < pages.length; i++) {
int page = pages[i];
int j;
for (j = 0; j < frames.length; j++) {
if (frames[j] == page) {
ref_bits[j] = true;
break;
}
if (frames[j] == 0) {
frames[j] = page;
ref_bits[j] = true;
faults++;
break;
}
}
if (j == frames.length) {
while (ref_bits[pointer]) {
ref_bits[pointer] = false;
pointer++;
if (pointer == frames.length) {
pointer = 0;
}
}
frames[pointer] = page;
ref_bits[pointer] = true;
pointer++;
if (pointer == frames.length) {
pointer = 0;
}
faults++;
}
System.out.print("Page " + page + ": ");
for (int k = 0; k < frames.length; k++) {
System.out.print(frames[k] + " ");
}
System.out.println();
}
System.out.println("Page faults: " + faults);
}
}
```