ArrayStack
ArrayStack.java 源码
package datastructure.stack;
import java.util.Arrays;
import java.util.EmptyStackException;
/**
* @author roseduan[roseduan520@gmail.com]
* @time 2019/10/27 15:13
* @description 使用数组实现简单的栈
*/
public class ArrayStack<T> {
private static final int DEFAULT_CAPACITY = 10;
private Object[] data;
private int capacity;
private int size;
public ArrayStack(int capacity) {
this.data = new Object[capacity];
this.capacity = capacity;
this.size = 0;
}
public ArrayStack(){
this(DEFAULT_CAPACITY);
}
/**
* 入栈
*/
public void push(T value){
//扩容
if (size >= capacity){
resize(data, capacity + (capacity >> 1));
}
data[size++] = value;
}
/**
* 出栈
*/
public T pop(){
if (size == 0){
throw new EmptyStackException();
}
T result = elementAt(size - 1);
data[--size] = null;
//缩容
if (size < capacity / 2){
resize(data, capacity >> 1);
}
return result;
}
/**
* 获取栈顶元素
*/
public T peek(){
if (size == 0){
throw new EmptyStackException();
}
return elementAt(size - 1);
}
@Override
public String toString() {
return Arrays.toString(data);
}
@SuppressWarnings("unchecked")
private T elementAt(int index){
if (index < 0 || index >= size){
throw new IllegalArgumentException("index " + index + " is illegal");
}
return (T) data[index];
}
/**
* 重新设置data，用于扩容和缩容
*/
private void resize(Object[] data, int newCapacity) {
this.data = Arrays.copyOf(data, newCapacity);
this.capacity = newCapacity;
}
}
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