近来复习数据结构，自己动手实现了栈。栈是一种限制插入和删除只能在一个位置上的表。最基本的操作是进栈和出栈，因此，又被叫作“先进后出”表。
实现方式是这样的：首先定义了一个接口，然后通过这个接口实现了线性栈和链式栈，代码比较简单，如下：
1 package com.peter.java.dsa.interfaces;
2
3 /**
4 * 栈操作定义
5 *
6 * @author Peter Pan
7 */
8
9 public interface Stack<T> {
10 /* 判空 */
11 boolean isEmpty();
12
13 /* 清空栈 */
14 void clear();
15
16 /* 弹栈 */
17 T pop();
18
19 /* 入栈 */
20 boolean push(T data);
21
22 /* 栈的长度 */
23 int length();
24
25 /* 查看栈顶的元素，但不移除它 */
26 T peek();
27
28 /* 返回对象在栈中的位置 */
29 int search(T data);
30 }
线性栈：以数组的方式实现。
1 package com.peter.java.dsa.common;
2
3 import com.peter.java.dsa.interfaces.Stack;
4
5 /**
6 * 线性栈
7 *
8 * @author Peter Pan
9 */
10 public class LinearStack<T> implements Stack<T> {
11 @SuppressWarnings("unchecked")
12 private T[] t = (T[]) new Object[16];
13 private int size = 0;
14
15 @Override
16 public boolean isEmpty() {
17 // TODO Auto-generated method stub
18 return size == 0;
19 }
20
21 @Override
22 public void clear() {
23 // TODO Auto-generated method stub
24 for (int i = 0; i < t.length; i++) {
25 t[i] = null;
26 }
27 size = 0;
28 }
29
30 @Override
31 public T pop() {
32 // TODO Auto-generated method stub
33 if (size == 0) {
34 return null;
35 }
36 T tmp = t[size - 1];
37 t[size - 1] = null;
38 size--;
39 return tmp;
40 }
41
42 @Override
43 public boolean push(T data) {
44 // TODO Auto-generated method stub
45 if (size >= t.length) {
46 resize();
47 }
48 t[size++] = data;
49 return true;
50 }
51
52 @Override
53 public int length() {
54 // TODO Auto-generated method stub
55 return size;
56 }
57
58 @Override
59 public T peek() {
60 // TODO Auto-generated method stub
61 if (size == 0) {
62 return null;
63 } else {
64 return t[size - 1];
65 }
66 }
67
68 /* return index of data, return -1 if no data */
69 @Override
70 public int search(T data) {
71 // TODO Auto-generated method stub
72 int index = -1;
73 for (int i = 0; i < t.length; i++) {
74 if (t[i].equals(data)) {
75 index = i;
76 break;
77 }
78 }
79 return index;
80 }
81
82 @SuppressWarnings("unchecked")
83 private void resize() {
84 T[] tmp = (T[]) new Object[t.length * 2];
85 for (int i = 0; i < t.length; i++) {
86 tmp[i] = t[i];
87 t[i] = null;
88 }
89 t = tmp;
90 tmp = null;
91 }
92
93 /* from the left to the right is from the top to the bottom of the stack */
94 @Override
95 public String toString() {
96 // TODO Auto-generated method stub
97 StringBuffer buffer = new StringBuffer();
98 buffer.append("Linear Stack Content:[");
99 for (int i = t.length - 1; i > -1; i--) {
100 buffer.append(t[i].toString() + ",");
101 }
102 buffer.append("]");
103 buffer.replace(buffer.lastIndexOf(","), buffer.lastIndexOf(",") + 1, "");
104 return buffer.toString();
105 }
106
107 }
链式栈：通过单链表进行实现。
1 package com.peter.java.dsa.common;
2
3 import com.peter.java.dsa.interfaces.Stack;
4
5 public class LinkedStack<T> implements Stack<T> {
6 private Node top;
7 private int size;
8
9 @Override
10 public boolean isEmpty() {
11 // TODO Auto-generated method stub
12 return size == 0;
13 }
14
15 @Override
16 public void clear() {
17 // TODO Auto-generated method stub
18 top = null;
19 size = 0;
20 }
21
22 @Override
23 public T pop() {
24 // TODO Auto-generated method stub
25 T topValue = null;
26 if (top != null) {
27 topValue = top.data;
28 Node oldTop = top;
29 top = top.prev;
30 oldTop.prev = null;
31 size--;
32 }
33 return topValue;
34 }
35
36 @Override
37 public boolean push(T data) {
38 // TODO Auto-generated method stub
39 Node oldTop = top;
40 top = new Node(data);
41 top.prev = oldTop;
42 size++;
43 return true;
44 }
45
46 @Override
47 public int length() {
48 // TODO Auto-generated method stub
49 return size;
50 }
51
52 @Override
53 public T peek() {
54 // TODO Auto-generated method stub
55 T topValue = null;
56 if (top != null) {
57 topValue = top.data;
58 }
59 return topValue;
60 }
61
62 @Override
63 public int search(T data) {
64 // TODO Auto-generated method stub
65 int index = -1;
66 Node tmp = top;
67 for (int i = size - 1; i > -1; i--) {
68 if (tmp.data.equals(data)) {
69 index = i;
70 break;
71 } else {
72 tmp = tmp.prev;
73 }
74 }
75 tmp = null;
76 return index;
77 }
78
79 @Override
80 public String toString() {
81 // TODO Auto-generated method stub
82 StringBuffer buffer = new StringBuffer();
83 buffer.append("Linked Stack Content:[");
84 Node tmp = top;
85 for (int i = 0; i < size - 1; i++) {
86 buffer.append(tmp.toString() + ",");
87 tmp = tmp.prev;
88 }
89 tmp = null;
90 buffer.append("]");
91 buffer.replace(buffer.lastIndexOf(","), buffer.lastIndexOf(",") + 1, "");
92 return super.toString();
93 }
94
95 private class Node {
96 T data;
97 Node prev;
98
99 public Node(T data) {
100 // TODO Auto-generated constructor stub
101 this.data = data;
102 }
103 }
104
105 }
学习还在进行中，以后会继续更新代码。
来源：https://www.cnblogs.com/littlepanpc/p/3436419.html