中缀表达式转为后缀表达式

//stack
public class StackX {
		
	private int top;
	private char[] stackArray;
	private int maxSize;
	
	//constructor
	public StackX(int maxSize){
		this.maxSize = maxSize;
		this.top = -1;
		stackArray = new char[this.maxSize];
	}
	//put item on top of stack
	public void push(char push){
		stackArray[++top] = push;
	}
	//take item from top of stack
	public char pop(){
		return stackArray[top--];
	}
	//peek the top item from stack
	public char peek(){
		return stackArray[top];
	}
	//peek the character at index n
	public char peekN(int index){
		return stackArray[index];
	}
	//true if stack is empty
	public boolean isEmpty(){
		return (top == -1);
	}
	//return stack size
	public int size(){
		return top+1;
	}	
}

//InToPost
public class InToPost {
	private StackX myStack;
	private String input;
	private String outPut="";
	//constructor
	public InToPost(String input){
		this.input = input;
		myStack = new StackX(this.input.length());
	}
	//do translation to postFix
	public String doTrans(){
		for(int i=0; i<input.length(); i++){
			char ch = input.charAt(i);
			switch(ch){
			case '+':
			case '-':
				this.getOper(ch,1);
				break;
			case '*':
			case '/':
				this.getOper(ch,2);
				break;
			case '(':
				this.getOper(ch, 3);
				break;
			case ')':
				this.getOper(ch, 4);
				break;
			default:
				this.outPut = this.outPut + ch;
			}
		}
		while(!this.myStack.isEmpty()){
			this.outPut = this.outPut + this.myStack.pop();
		}
		return this.outPut;
	}
	//get operator from input
	public void getOper(char ch, int prect1){
		char temp;
		if(this.myStack.isEmpty()||prect1==3){
			this.myStack.push(ch);
		}
		else if(prect1==4){
			while(!this.myStack.isEmpty()){
				temp = this.myStack.pop();
				if(temp=='(')continue;
				this.outPut = this.outPut + temp;
			}
		}
		else if(prect1==1){
			temp = this.myStack.peek();
			if(temp=='(') this.myStack.push(ch);
			else{
				this.outPut = this.outPut + this.myStack.pop();
				this.myStack.push(ch);
			}
		}
		else{
			temp = this.myStack.peek();
			if(temp=='('||temp=='+'||temp=='-') this.myStack.push(ch);
			else{
				this.outPut = this.outPut + this.myStack.pop();
			}
		}
	}
}
//Test

public class TestInToPost {
	private static InToPost inToPost;
	private static String str;
	
	public static void main(String []args){
		str = "((A+B)*C)-D";
		inToPost = new InToPost(str);
		System.out.println(inToPost.doTrans());
	}
}

 算法实现不是很完善，有些复杂的表达式解析要出错，写出来做个纪念！