Java数据结构与算法(3)

栈的基本特性是后进先出，最简单的用途是用于转置，还有其他诸如括号匹配，中序表达式(A+B*(C-D/(E+F)) --> ABCDEF+/-*+)和后续表达式(345+*612+/- --> 3*(4+5)-6/(1+2))互换等高级用法。

示例代码：

package chap04.Reverse;

import java.io.*; // for I/O

class StackX {
    private int maxSize;
    private char[] stackArray;
    private int top;

    public StackX(int max) {
        maxSize = max;
        stackArray = new char[maxSize];
        top = -1;
    }

    public void push(char j) {
        stackArray[++top] = j;
    }

    public char pop() {
        return stackArray[top--];
    }

    public char peek() {
        return stackArray[top];
    }

    public boolean isEmpty() {
        return (top == -1);
    }
    
    public boolean isFull() {
        return (top == maxSize - 1);
    }
}  

class Reverser {
    private String input;  
    private String output;  

    public Reverser(String in) {
        input = in;
    }

    // 转置
    public String doRev() {
        int stackSize = input.length();  
        StackX theStack = new StackX(stackSize);  

        for (int j = 0; j < input.length(); j++) {
            char ch = input.charAt(j);  
            theStack.push(ch);  
        }
        output = "";
        while (!theStack.isEmpty()) {
            char ch = theStack.pop();  
            output = output + ch;  
        }
        return output;
    }  
}  

class ReverseApp {
    public static void main(String[] args) throws IOException {
        String input, output;
        while (true) {
            System.out.print("Enter a string: ");
            System.out.flush();
            input = getString1();  
            if (input.equals("")) {  
                break;
            }

            Reverser theReverser = new Reverser(input);
            output = theReverser.doRev(); 
            System.out.println("Reversed: " + output);
        } 
    } 

    public static String getString1() throws IOException {
        InputStreamReader isr = new InputStreamReader(System.in);
        BufferedReader br = new BufferedReader(isr);
        String s = br.readLine();
        return s;
    }
}