java 实现 stack详解及实例代码

public class MyArrayStack<E> {

 private ArrayList<E> list = new ArrayList<>();

 public void push(E e) {
 list.add(e);
 }

 public E pop() {
 return list.remove(list.size() - 1);
 }

 public E peek() {
 return list.get(list.size() - 1);
 }

 public boolean isEmpty() {
 return list.size() == 0;
 }
}

public class MyLinkStack<E> {

 LinkedList<E> list = new LinkedList<>();

 public void push(E e) {
 list.addLast(e);
 }

 public E pop() {
 return list.removeLast();
 }

 public E peek() {
 return list.getLast();
 }

 public boolean isEmpty() {
 return list.size() == 0;
 }
}

public class BalanceSymbol {

 public boolean isBalance(String string) {
 MyArrayStack<Character> stack = new MyArrayStack<>();
 char[] array = string.toCharArray();
 for (char ch : array) {
  if ("{[(".indexOf(ch) >= 0) {
  stack.push(ch);
  } else if ("}])".indexOf(ch) >= 0) {
  if (isMatching(stack.peek(), ch)) {
   stack.pop();
  }
  }
 }

 return stack.isEmpty();
 }

 private boolean isMatching(char peek, char ch) {
 if ((peek == '{' && ch == '}') || (peek == '[' && ch == ']') || (peek == '(' && ch == ')')) {
  return true;
 }
 return false;
 }

 public static void main(String[] args) {
 BalanceSymbol symbol = new BalanceSymbol();
 String string = "public static void main(String[] args) {BalanceSymbol symbol = new BalanceSymbol();}";
 String string2 = "public static void main(String[] args) {BalanceSymbol symbol = new BalanceSymbol([);}]";
 System.out.println(symbol.isBalance(string));
 System.out.println(symbol.isBalance(string2));
 }
}

/**
 * 简化版本，每个操作数只一位，并且假设字符串合法
 */
public class PostfixExpression {

 public static int calculate(String string) {
 MyArrayStack<String> stack = new MyArrayStack<>();

 char[] arr = string.toCharArray();

 for (char ch : arr) {
  if ("0123456789".indexOf(ch) >= 0) {
  stack.push(ch + "");
  } else if ("+-*/".indexOf(ch) >= 0) {
  int a = Integer.parseInt(stack.pop());
  int b = Integer.parseInt(stack.pop());
  if (ch == '+') {
   stack.push((a + b) + "");
  } else if (ch == '-') {
   stack.push((a - b) + "");
  } else if (ch == '*') {
   stack.push((a * b) + "");
  } else if (ch == '/') {
   stack.push((a / b) + "");
  }
  }
 }
 return Integer.parseInt(stack.peek());
 }

 public static void main(String[] args) {
 System.out.println(calculate("32+32*+"));
 }
}

import java.util.HashMap;
import java.util.Map;

public class ExpressionSwitch {

 private static Map<Character, Integer> map = new HashMap<Character, Integer>();

 static {
 map.put('+', 0);
 map.put('-', 1);
 map.put('*', 2);
 map.put('/', 3);
 map.put('(', 4);
 }

 private static char[][] priority = {
  // 当前操作符
  //    +  -  *  /  ( 
  /* 栈 + */{ '>', '>', '<', '<', '<'},
  /* 顶 - */{ '>', '>', '<', '<', '<'},
  /* 操 * */{ '>', '>', '>', '>', '<'},
  /* 作 / */{ '>', '>', '>', '>', '<'},
     /* 符 ( */{ '<', '<', '<', '<', '<'},
 };

 public static String switch1(String string) {
 StringBuilder builder = new StringBuilder();

 char[] arr = string.toCharArray();

 MyArrayStack<Character> stack = new MyArrayStack<>();
 for (char ch : arr) {
  if ("0123456789abcdefghijklmnopqrstuvwxyz".indexOf(ch) >= 0) {
  builder.append(ch);
  } else if ('(' == ch) {
  stack.push(ch);
  } else if (')' == ch) {
  while (true && !stack.isEmpty()) {
   char tmp = stack.pop();
   if (tmp == '(') {
   break;
   } else {
   builder.append(tmp);
   }
  }
  } else {
  while (true) {
   if (stack.isEmpty()) {
   stack.push(ch);
   break;
   }
   char tmp = stack.peek();
   if (isPriorityHigh(tmp, ch)) {
   builder.append(stack.pop());
   } else {
   stack.push(ch);
   break;
   }
  }
  }
 }

 while(!stack.isEmpty()) {
  builder.append(stack.pop());
 }

 return builder.toString();
 }

 private static boolean isPriorityHigh(char tmp, char ch) {
 return priority[map.get(tmp)][map.get(ch)] == '>';
 }

 public static void main(String[] args) {
 System.out.println(switch1("a+b*c-(d*e+f)/g"));
 }
}