Merge pull request larissalages#274 from ashutosh321607/master

added stack DS

Author: larissalages

data_structures/Java/stack/stack.java

@@ -0,0 +1,87 @@
+import java.lang.Math;
+public class Mystack implements Stack{
+  Object data[];
+  int top=0,cap;
+  Mystack(int size){
+    data = new Object[size];
+    cap = size;
+  }
+  public boolean IsFull(){
+    if(top==cap){
+      return true;
+    }
+    return false;
+  }
+  public boolean IsEmpty(){
+    if(top == 0){
+      return true;
+    }
+    return false;
+  }
+  public void Push(Object ele){
+    if(IsFull()){
+      System.out.println("Stack is Full, Can't add more elemeants.");
+    }
+    data[top] = ele;
+    top++;
+    System.out.println("Element added.");
+  }
+  public Object Pop(){
+    if(IsEmpty()){
+      System.out.println("Stack is empty, add element first.");
+      return -1;
+    }
+    top--;
+    return data[top];
+  }
+  public Object peek(){
+    if(IsEmpty()){
+      System.out.println("Stack is empty, add element first.");
+      return -1;
+    }
+    return data[top-1];
+  }
+
+  public int Prec(char ele){
+    switch(ele){
+      case '+': 
+      case '-': 
+        return 1; 
+     
+      case '*': 
+      case '/': 
+        return 2; 
+     
+      case '^': 
+        return 3; 
+    }
+    return -1;
+  }
+
+  public Object opration(int b,int a,char c){
+    switch(c){
+      case '+':
+        return a+b;
+      case '-':
+        return a-b;                 
+      case '*':
+        return a*b;
+      case '/':
+        return a/b;
+      // case '^':
+      //   int n=1;
+      //   boolean x=true;
+      //   if(a==0)
+      //     x=false;
+      //   while(x){
+      //     n*=a;
+      //     a--;
+      //     if(a>0)
+      //       x=false;
+      //   }
+      //   return n;
+      default:
+        return -1;
+    }
+  }
+}