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@larswaechter
Last active Dec 16, 2021
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Generic Stack Implementation in Java
class Stack<T> implements Stackable<T> {
private Stack<T> previous;
private T value;
Stack() {
}
Stack(T value) {
this.value = value;
}
Stack(Stack<T> previous, T value) {
this.previous = previous;
this.value = value;
}
@Override
public void push(T value) {
if (this.value == null)
this.value = value;
else {
this.previous = new Stack<T>(this.previous, this.value);
this.value = value;
}
}
@Override
public T pop() {
if (this.isEmpty())
throw new IllegalArgumentException("Stack is empty");
T top = this.value;
this.value = this.previous.value;
this.previous = this.previous.previous;
return top;
}
@Override
public T peek() {
return this.value;
}
@Override
public boolean isEmpty() {
return this.previous == null;
}
@Override
public int size() {
return this.isEmpty() ? 0 : 1 + this.previous.size();
}
@Override
public int search(Object o) {
int count = 1;
for (Stack<T> stack = this; !stack.isEmpty(); stack = stack.previous) {
if (stack.value.equals(o))
return count;
count++;
}
return -1;
}
@Override
public String toString() {
if (!this.isEmpty())
return this.previous + " <- " + this.value;
return this.value != null ? String.valueOf(this.value) : "";
}
}
interface Stackable<T> {
void push(T value);
T pop();
T peek();
boolean isEmpty();
int size();
int search(Object o);
}
@Bheniamyn
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Bheniamyn commented Dec 16, 2021

Smart, simple and efficient solution, I like it, thanks! :)

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