adding program for conversion

conversion.java

@@ -0,0 +1,122 @@
+class myStack {
+    static final int MAX = 10;
+    int top;
+    char[] a = new char[MAX];
+
+    myStack() {
+        top = -1;
+    }
+
+    boolean push(char x) {
+        if (top >= (MAX - 1)) {
+            System.out.println("Stack Overflow");
+            return false;
+        } else {
+            a[++top] = x;
+            return true;
+        }
+    }
+
+    int pop() {
+        if (top < 0) {
+            System.out.println("Stack Underflow");
+            return Integer.MIN_VALUE;
+        } else {
+            int x = a[top--];
+            return x;
+        }
+    }
+
+    char peek() {
+        if (top < 0) {
+            System.out.println("Stack Underflow");
+            return 0;
+        } else {
+            char x = a[top];
+            return x;
+        }
+    }
+
+    int size() {
+        return (top + 1);
+    }
+
+    boolean isEmpty() {
+        return top == -1;
+    }
+
+    boolean isFull() {
+        return top == MAX - 1;
+    }
+}
+
+class conversion {
+    static boolean checkIfOperand(char ch) {
+        return Character.isLetterOrDigit(ch);
+    }
+
+    static int precedence(char ch) {
+        switch (ch) {
+            case '+':
+            case '-':
+                return 1;
+            case '*':
+            case '/':
+                return 2;
+            case '^':
+                return 3;
+        }
+        return -1;
+    }
+
+    static void covertInfixToPostfix(String expr) {
+        int i;
+        myStack s = new myStack();
+        StringBuilder result = new StringBuilder(new String(""));
+        for (i = 0; i < expr.length(); ++i) {
+            if (checkIfOperand(expr.charAt(i)))
+                result.append(expr.charAt(i));
+            else if (expr.charAt(i) == '(' || expr.charAt(i) == '[' || expr.charAt(i) == '{')
+                s.push(expr.charAt(i));
+            else if (expr.charAt(i) == ')' || expr.charAt(i) == ']' || expr.charAt(i) == '}') {
+                if (expr.charAt(i) == ')') {
+                    while (!s.isEmpty() && s.peek() != '(') {
+                        result.append(s.peek());
+                        s.pop();
+                    }
+                    s.pop();
+                }
+                if (expr.charAt(i) == ']') {
+                    while (!s.isEmpty() && s.peek() != '[') {
+                        result.append(s.peek());
+                        s.pop();
+                    }
+                    s.pop();
+                }
+                if (expr.charAt(i) == '}') {
+                    while (!s.isEmpty() && s.peek() != '{') {
+                        result.append(s.peek());
+                        s.pop();
+                    }
+                    s.pop();
+                }
+            } else {
+                while (!s.isEmpty() && precedence(expr.charAt(i)) <= precedence(s.peek())) {
+                    result.append(s.peek());
+                    s.pop();
+                }
+                s.push(expr.charAt(i));
+            }
+        }
+        while (!s.isEmpty()) {
+            result.append(s.peek());
+            s.pop();
+        }
+        System.out.println(result);
+    }
+
+    public static void main(String[] args) {
+        String expression = "A+B*(C^D-E)";
+        covertInfixToPostfix(expression);
+    }
+}