Programming Examples

Java Program to evaluate mathematical expressions in String

java8

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
public class Main {
	public static void main(String[] args) throws Exception {
		ScriptEngineManager scriptEngineManager  = new ScriptEngineManager();
		ScriptEngine scriptEngine = scriptEngineManager.getEngineByName("JavaScript");
		// JavaScript code from String
		Object ob = scriptEngine.eval("9 + 15 + 30");
		System.out.println("Result of evaluating mathematical expressions in String = "+ob);
	}
}

vector insert() function in C++ STL

cpp

#include<iostream>
#include <bits/stdc++.h>
using namespace std;

int main() {
   vector<int> v = { 50,60,70,80,90},v1;        //declaring v(with values), v1 as vector.
   vector<int>::iterator iter;                  //declaring an iterator
   iter = v.insert(v.begin(), 40);              //inserting a value in v vector before the beginning.
   iter = v.insert(v.begin(), 1, 30);           //inserting a value with its size in v vector before the beginning.
   cout << "The vector1 elements are: \n";
   for (iter = v.begin(); iter != v.end(); ++iter)
      cout << *iter << " "<<endl;             // printing the values of v vector
   v1.insert(v1.begin(), v.begin(), v.end()); //inserting all values of v in v1 vector.
   cout << "The vector2 elements are: \n";
   for (iter = v1.begin(); iter != v1.end(); ++iter)
      cout << *iter << " "<<endl;            // printing the values of v1 vector
   return 0;
}

Set vs Map in C++ STL

cpp

#include<iostream>
#include <bits/stdc++.h>
using namespace std;

int main()
{
   map<char, int> m;                     //initialize a map
   map<char, int>::iterator iter;       //initializing a map as iterator
   m.insert (pair<char, int>('a', 10)); //inserting values to the map
   m.insert (pair<char, int>('b', 20));

   cout << "Elements in map:\n";
   for (iter=m.begin();iter!=m.end();iter++)
   cout << "[ " << iter->first << ", "<< iter->second << "]\n"; //printing the values of the map
   return 0;
}

C++ STL Priority Queue for Structure or Class

cpp

#include <iostream>
#include <queue>
using namespace std;
#define ROW 6
#define COL 3
struct student { //defining the student structure
   int roll,marks;
   student(int roll, int marks)
      : roll(roll), marks(marks)
   {
   }
};
struct comparemarks{ // defining the comparemarks structure
   bool operator()(student const& s1, student const& s2)
   //overloading the operators of the student structure
   {
      return s1.marks < s2.marks;
   }
};
int main()
{
   priority_queue<student, vector<student>, comparemarks> M;
   // using the priority queue.
   // We have to use this type of syntax to use the priority queue.
   int a[ROW][COL] = {{15, 50}, {16, 60},
   {18,70}, {14, 80}, {12, 90}, {20, 100}};
   for (int i = 0; i < ROW; ++i) {
      M.push(student(a[i][0], a[i][1])); //inserting variables in       the queue
   }
   cout<<"priority queue for structure ::"<<endl;
   while (!M.empty()) {
      student s = M.top();
      M.pop();
      cout << s.roll << " " << s.marks << "\n"; //printing the values
   }
   return 0;
}

C++ set lower_bound() function

cpp

#include<iostream>
#include <bits/stdc++.h>
using namespace std;
int main()
{
   set<int> s;                 //Declaring an empty set container
   set<int>::iterator iter;    //Declaring a set container as iterator which will point to the lower bound value
   s.insert(7);                //inserting elements in the set container s
   s.insert(6);
   s.insert(1);
   s.insert(4);
   s.insert(2);
   s.insert(9);
   s.insert(10);
   iter = s.lower_bound(4);       //passing a key by parameter to find its lower bound
      cout <<"The lower bound of 4 is: "<< *iter << " "<<endl; //printing the lowerbound value
   iter = s.lower_bound(5);
      cout <<"The lower bound of 5 is: " <<*iter << " "<<endl;
   iter = s.lower_bound(30);
      cout <<"The lower bound of 30 is: " <<*iter << " "<<endl;

return 0;
    
}

Java equals() method

java8

public class Sample {
   public static void main(String []args) {
      String s1 = "tutorialspoint";
      String s2 = "tutorialspoint";
      String s3 = new String ("Tutorials Point");
      System.out.println(s1.equals(s2));
      System.out.println(s2.equals(s3));
   }
}

Java Program to Compare Two Strings

java8

import java.lang.*;
public class StringDemo {
   public static void main(String[] args) {
      String str1 = "tutorials", str2 = "point";
      // comparing str1 and str2
      int retval = str1.compareTo(str2);
      // prints the return value of the comparison
      if (retval < 0) {
         System.out.println("str1 is greater than str2");
      }
      else if (retval == 0) {
         System.out.println("str1 is equal to str2");
      }
      else {
         System.out.println("str1 is less than str2");
      }
   }
}

Java String equals() method

java8

public class Sample{
   public static void main(String []args){
      String s1 = "tutorialspoint";
      String s2 = "tutorialspoint";
      String s3 = new String ("Tutorials Point");
      System.out.println(s1.equals(s2));
      System.out.println(s2.equals(s3));
   }
}

String compare by equals() method in Java

java8

public class Test {
   public static void main(String args[]) {
      Integer x = 5;
      Integer y = 10;
      Integer z =5;
      Short a = 5;
      System.out.println(x.equals(y));
      System.out.println(x.equals(z));
      System.out.println(x.equals(a));
   }
}

Append method in Java

java8

import java.lang.*;
public class StringBufferDemo {
   public static void main(String[] args) {
      StringBuffer buff = new StringBuffer("tuts ");
      System.out.println("buffer = " + buff);
     
      // appends the char argument as string to the string buffer.
      buff.append('A');
     
      // print the string buffer after appending
      System.out.println("After append = " + buff);
      buff = new StringBuffer("abcd ");
      System.out.println("buffer = " + buff);
     
      // appends the char argument as string to the string buffer.
      buff.append('!');
     
      // print the string buffer after appending
      System.out.println("After append = " + buff);
   }
}

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