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public class Stack<E> {
private Object[] data = null ;
private int maxStack = 0;
private int top = -1;
Stack(){
this(10);
}
Stack (int initialSize){
if (initialSize >= 0) {
this.maxStack = initialSize;
data = new Object[initialSize];
top = -1;
}else {
throw new RuntimeException("can't create stack'"+ initialSize);
}
}
public boolean push(E e){
if (top == maxStack -1){
throw new RuntimeException("can't push stack'");
}else {
data[++top] = e;
return true;
}
}
public E pop() {
if (top == -1 ) {
throw new RuntimeException("stack is empty");
}else {
return (E)data[top--];
}
}
public E peek() {
if (top == -1){
throw new RuntimeException("stack is empty");
}else{
return (E)data[top];
}
}
}
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