Java-Part 0

Advanced Java and Cutting-edge Applications

Part 0: Course presentation

Part 1

其实就是个括号匹配问题，Stack 经典问题，但是好久没用Java，有一点点生疏，感觉老师的版本要简洁的多

java">package tiei.ajp.test;import java.util.HashMap;
import java.util.Map;
import java.util.Stack;public class CheckBalance {public String str;public CheckBalance() {}public CheckBalance(String string) {str = string;}public boolean balanced() {Stack<Character> stack = new Stack<>();char[] s = str.toCharArray();Map<Character, Integer> map = Map.of('(', 1, '[', 2, '{', 3, ')', 4, ']', 5, '}', 6);for (Character c : s) {
//            if ((c != '(') && (c != ')') && (c != '[') && (c != ']') && (c != '{') && (c != '}')) continue;if(!map.containsKey(c)) continue;
//            if (c == '(' || c == '{' || c == '[') {if (map.get(c) <= map.size() / 2) {stack.push(c);} else {if (stack.empty()) return false;char temp = stack.peek();
//                if ((temp == '(' && c == ')') || (temp == '[' && c == ']') || (temp == '{' && c == '}')) {if (map.get(c) - map.get(temp) == map.size() / 2) {stack.pop();} else {return false;}}}return stack.empty();}public int index() {Stack<Integer> stack = new Stack<>();char[] s = str.toCharArray();for (int i = 0; i < s.length; i++) {char c = s[i];
//            if (Character.isLetter(c) || c == ' ') continue;if ((c != '(') && (c != ')') && (c != '[') && (c != ']') && (c != '{') && (c != '}')) continue;if (c == '(' || c == '{' || c == '[') {stack.push(i);} else {if (stack.empty()) return i;char temp = s[stack.peek()];if ((temp == '(' && c == ')') || (temp == '[' && c == ']') || (temp == '{' && c == '}')) {stack.pop();} else {return i;}}}if (!stack.empty()) return stack.peek();return -1;}
}

老师版本：

java">package tiei.ajp.test;import java.util.HashMap;
import java.util.Map;
import java.util.Stack;public class CheckBalance {private final String OPENINGS = "([{";private final String CLOSINGS = ")]}";private String s;private int index;private boolean balanced;public CheckBalance(String str) {this.s = str;balanced = balancedPrivate();}public boolean balanced(){return balanced;}private boolean balancedPrivate() {index = 0;Stack<Character> stack = new Stack<>();for (index = 0; index < s.length(); index++) {char c = s.charAt(index);if (isOpening(c)) {stack.push(c);} else if (isClosing(c)) {if (stack.empty() || dontMatch(stack.pop(), c)) {return false;}}}return stack.isEmpty();}public int index() {return index;}private boolean isOpening(char c) {return OPENINGS.indexOf(c) > -1;}private boolean isClosing(char c) {return CLOSINGS.indexOf(c) > -1;}private boolean dontMatch(char o, char c) {return OPENINGS.indexOf(o) != CLOSINGS.indexOf(c);}
}

Part 2

java">package tiei.ajp.test;public class ArrayStack {private static int MAX_SIZE = 100;private char[] stackArray;private int top;public ArrayStack(){stackArray = new char[MAX_SIZE];top = -1; }public boolean isEmpty(){return top == -1;}public char peek(){if (isEmpty()) {return '\0';}return stackArray[top];}public void push(char c){if (top < MAX_SIZE - 1) {stackArray[++top] = c;}}public char pop(){if (isEmpty()) {return '\0';}return stackArray[top--];}
}

Part 3

java">package tiei.ajp.test;public class ListStack {private class Node {char data;Node next;Node(char data) {this.data = data;this.next = null;}}private Node top;public ListStack() {top = null;}public boolean isEmpty() {return top == null;}public char peek() {if (isEmpty()) {return '\0';}return top.data;}public void push(char c) {Node newNode = new Node(c);newNode.next = top;top = newNode;}public char pop() {if (isEmpty()) {return '\0';}char popData = top.data;top = top.next;return popData;}
}

Test code

java">//
// Advanced Java Programming
// TIEI - Fall 2024
//
package tiei.ajp.test;import java.util.*;
import tiei.ajp.test.CheckBalance;/*** A TestCheckBalance class for the test* YOU MUST NOT CHANGE THIS CLASS!!!*/
public class TestCheckBalance {// the expected answers from the userprivate static final String YES = "yes";private static final String NO  = "no";/*** The main program*/public static void main(String[] args) {Scanner input = new Scanner(System.in);System.out.println("Welcome to the Balance Checking Program");do {System.out.print("\nEnter the string you wish to check: ");String theString = input.nextLine();CheckBalance check = new CheckBalance(theString);if ( check.balanced() )System.out.println("The string is balanced!");else {System.out.println("The string is unbalanced:\n");System.out.println(theString);System.out.printf("%" + ( check.index() + 2 ) + "s", "^\n");}System.out.println();} while ( more(input) );}// Ask the user for more and return a booleanprivate static boolean more(Scanner input) {String answer = null;do {System.out.print("More ('" + YES + "' or '" + NO + "')? ");answer = input.nextLine().trim().toLowerCase();} while ( ! answer.equals(YES) && ! answer.equals(NO) );return answer.equals(YES);}
}