数据结构和算法篇-环形缓冲区

完整实现

package com.madooei.cb.circulards;import com.madooei.cb.exception.EmptyException;public class CircularBuffer<T> {private T[] data;private int numElements;private int writePos; // 写指针(可认为是队尾)private int readPos; // 读指针(可认为是队首)// Constructor: create buffer with given capacitypublic CircularBuffer(int capacity){this.data = (T[])new Object[capacity];this.numElements = 0;this.writePos = 0;this.readPos = 0;}// Add element to buffer (overwrites oldest if full)public void write(T element){writePos = (readPos + numElements) % data.length;data[writePos] = element;if (isFull()) {// 当缓冲区已满时，写入新元素不仅要前移写指针，还需要**同步前移读指针**，以确保新的写入位置始终有效，// 并维持先进先出的顺序。readPos = (readPos + 1) % data.length;}else {numElements++;}}// Remove and return oldest elementpublic T read(){if (isEmpty()) {throw new EmptyException("You can not read from empty circular buffer");}T elemnt = data[readPos];readPos = (readPos + 1) % data.length;numElements--;return elemnt;}// Check if buffer is emptypublic boolean isEmpty() {return numElements == 0;}// Check if buffer is fullpublic boolean isFull(){return numElements >= data.length;}// Get current number of elementspublic int size(){return numElements;}// 查看当前队首的元素，不删除public T peek(){if (isEmpty()) {throw new EmptyException("You can not peek from empty circular buffer");}return data[readPos];}
}

测试用例

package com.madooei.cb.circulards;import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;public class CircularBufferTest {@Testpublic void test(){CircularBuffer<String> buffer = new CircularBuffer<>(3);buffer.write("A");buffer.write("B");buffer.write("C");// Buffer: [A, B, C] (full)Assertions.assertEquals("A", buffer.peek());buffer.write("D");  // Overwrites "A"// Buffer: [D, B, C] conceptually, but A is overwrittenAssertions.assertEquals("B", buffer.peek());String first = buffer.read();  // Returns "B"Assertions.assertEquals("B", first);Assertions.assertEquals("C", buffer.peek());String second = buffer.read(); // Returns "C"Assertions.assertEquals("C", second);// Buffer now contains just "D"buffer.write("E");buffer.write("F");Assertions.assertEquals("D", buffer.peek());buffer.write("G");Assertions.assertEquals("E", buffer.peek());}
}

环形缓冲区示例用法

CircularBuffer<String> buffer = new CircularBuffer<>(3);buffer.write("A");
buffer.write("B");
buffer.write("C");
// Buffer: [A, B, C] (full)buffer.write("D");  // Overwrites "A"
// Buffer: [D, B, C] conceptually, but A is overwrittenString first = buffer.read();  // Returns "B"
String second = buffer.read(); // Returns "C"
// Buffer now contains just "D"buffer.write("E");
buffer.write("F");
// Buffer: [D, E, F]

示例追踪

CircularBuffer<String> buffer = new CircularBuffer<>(3);数组：[][][]
写指针`back`：0
读指针`front`：0
numElements:0buffer.write("A");
数组：[A][][]
写指针`back`：1
读指针`front`：0
numElements:1buffer.write("B");
数组：[A][B][]
写指针`back`：2
读指针`front`：0
numElements:2buffer.write("C");
// Buffer: [A, B, C] (full)
数组：[A][B][C]
写指针`back`：0
读指针`front`：0
numElements:3buffer.write("D");  // Overwrites "A"
数组：[D][B][C]
写指针`back`：1 // 前移写指针
读指针`front`：1 // 前移读指针
numElements:3// Buffer: [D, B, C] conceptually, but A is overwrittenString first = buffer.read();  // Returns "B"
数组：[D][null][C]
写指针`back`：1
读指针`front`：2 // 前移读指针
numElements:2String second = buffer.read(); // Returns "C"
数组：[D][null][null]
写指针`back`：1
读指针`front`：0 // 前移读指针
numElements:1
// Buffer now contains just "D"buffer.write("E");
数组：[D][E][null]
写指针`back`：2
读指针`front`：0
numElements:2buffer.write("F");
数组：[D][E][F]
写指针`back`：0
读指针`front`：0
numElements:3
// Buffer: [D, E, F]buffer.write("G");
数组：[G][E][F]
写指针`back`：1
读指针`front`：1 // 前移读指针
numElements:3
// Buffer: [G, E, F]