public class StackClass<T> implements StackADT<T>
{
private int maxStackSize; //variable to store the
//maximum stack size
private int stackTop; //variable to point to
//the top of the stack
private T[] list; //array of reference variables
//Default constructor
//Create an array of the size 100 to implement the stack.
//Postcondition: The variable list contains the base
// address of the array, stackTop = 0,
// and maxStackSize = 100.
public StackClass()
{
maxStackSize = 100;
stackTop = 0; //set stackTop to 0
list = (T[]) new Object[maxStackSize]; //create the array
}//end default constructor
//Constructor with a parameter
//Create an array of the size stackSize to implement the
//stack.
//Postcondition: The variable list contains the base
// address of the array, stackTop = 0,
// and maxStackSize = stackSize.
public StackClass(int stackSize)
{
if (stackSize <= 0)
{
System.err.println("The size of the array to "
+ "implement the stack must be "
+ "positive.");
System.err.println("Creating an array of the size 100.");
maxStackSize = 100;
}
else
maxStackSize = stackSize; //set the stack size to
//the value specified by
//the parameter stackSize
stackTop = 0; //set stackTop to 0
list = (T[]) new Object[maxStackSize]; //create the array
}//end constructor
//Method to initialize the stack to an empty state.
//Postcondition: stackTop = 0
public void initializeStack()
{
for (int i = 0; i < stackTop; i++)
list[i] = null;
stackTop = 0;
}//end initializeStack
//Method to determine whether the stack is empty.
//Postcondition: Returns true if the stack is empty;
// otherwise, returns false.
public boolean isEmptyStack()
{
return (stackTop == 0);
}//end isEmptyStack
//Method to determine whether the stack is full.
//Postcondition: Returns true if the stack is full;
// otherwise, returns false.
public boolean isFullStack()
{
return (stackTop == maxStackSize);
}//end isFullStack
//Method to add newItem to the stack.
//Precondition: The stack exists and is not full.
//Postcondition: The stack is changed and newItem
// is added to the top of stack.
// If the stack is full, the method
// throws StackOverflowException
public void push(T newItem) throws StackOverflowException
{
if (isFullStack())
throw new StackOverflowException();
list[stackTop] = newItem; //add newItem at the
//top of the stack
stackTop++; //increment stackTop
}//end push
//Method to return a reference to the top element of
//the stack.
//Precondition: The stack exists and is not empty.
//Postcondition: If the stack is empty, the method
// throws StackUnderflowException;
// otherwise, a reference to the top
// element of the stack is returned.
public T peek() throws StackUnderflowException
{
if (isEmptyStack())
throw new StackUnderflowException();
return (T) list[stackTop - 1];
}//end peek
//Method to remove the top element of the stack.
//Precondition: The stack exists and is not empty.
//Postcondition: The stack is changed and the top
// element is removed from the stack.
// If the stack is empty, the method
// throws StackUnderflowException
public void pop() throws StackUnderflowException
{
if (isEmptyStack())
throw new StackUnderflowException();
stackTop--; //decrement stackTop
list[stackTop] = null;
}//end pop
}
我正在尝试实现一个reverseStack操作,该操作将一个堆栈的元素以相反的顺序复制到另一个堆栈上。到目前为止,我已经提出了以下内容...
public void reverseStack(StackClass<T> otherStack)
{
StackClass<T> newStack = new StackClass<T>();
StackObj obj = null;
while ( (obj = this.pop()) != null ) {
otherStack.push(obj);
newStack.push(obj);
}
// Now push back from newStack to this stack
while ( (obj = newStack.pop() ) != null ) {
this.push(obj);
}
}
但是我的代码部分有问题
StackObj obj = null;
while ( (obj = this.pop()) != null ) {
otherStack.push(obj);
newStack.push(obj);
}
因为 StackObj 类从未定义过。然而,我不知道还可以将 obj 定义为什么,因为我的 pop 过程不返回值。有什么想法吗?
谢谢(不,这不是家庭作业...我正在尝试通过练习自学 Java)。
最佳答案
您可以像这样直接使用类型 T:
public StackClass<T> reverseStack()
{
StackClass<T> newStack = new StackClass<T>();
T obj = null;
while ( (obj = this.pop()) != null ) {
newStack.push(obj);
}
return newStack; //Shallow reversed stack
}
由于您的堆栈包含 T 类型的对象,因此您也应该像 T 一样威胁它们。
需要记住的事情Deep vs Shallow Copy 。你正在做一个浅拷贝,这是你想要的吗? :)
关于java - Java中如何实现栈的反转?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/31667936/