Putting one string into another string java

Question

I am trying to stick one string into the middle of another string, and then put Monkey into the middle of the new string.

String One = "MonkeyPony";
String Two = "Monkey";

Basically what I'm trying to do is insert "Monkey" into the middle of "MonkeyPony" numerous times, so on the first time it would read "MonkeMonkeyyPony" on the second time it would read "MonkeMonMonkeykeyyPony", etc.

Answer 1

Use a StringBuilder:

StringBuilder builder = new StringBuilder(One);
for (int i = 0; i < 10; ++i) {
  builder.insert(builder.length() / 2, Two);
  System.out.println(builder.toString());
}

Answer 2

You can try this:

One = One.substr(0,One.length()/2)+Two+One.substr(One.length()/2+1, One.length();

The first element in the string concatenation takes the first half of the string One, and then you concatenate with thw word Two, and then add the rest of the one.

Answer 3

I don't know this question is from your real work or is homework/ interview algorithm question.

The straightforward solution would be calculating the index of original string, inserting the new string to that position. Do this n times.

I just write an idea, not sure if it is ok: say we want to do insert 100(n) times

• first we take the string two, the Monkey
• build two strings, one is "Mon" repeated 99 times (n-1), and the other one is "key", also repeat 99 times
• find out the insertion index of string ONE, say i
• insert this string to i position: 99Mons + String TWO("Monkey") + 99keys

I am not sure if this is a good way to go...

---

Did a small test:

I am curious about the performance of my solution, so I did a small performance test, with the straightforward solution from @Ame Burmeister.

In my test:

• Tests are done with Junit Test class
• StopWatch is from guava
• warming up 4 times before measuring elapsed time, to avoid Jit
• the two methods give same output (with smaller n), both are correctly implemented.
• Both tested with 100000 Insertions

The straightforward solution (Basically just copy from @Ame's answer)

@Test
    public void insertWithBuilder() {
        final int n = 100000;
        final String one = "MonkeyPony";
        final String two = "Monkey";

        final Stopwatch sw = new Stopwatch();
        int x = 1;
        for (; x <= 5; x++) {// loop 4 times (warming up) to avoid JIT
            if (x == 5) {
                sw.start();
            }
            final StringBuilder builder = new StringBuilder(one);
            System.out.println("warming up times:" + x);
            for (int i = 0; i < n; ++i) {
                builder.insert(builder.length() / 2, two);
            }
            if (x == 5) {
                sw.stop();
                // System.out.println("builder:" + builder.toString());
            }
        }
        System.out.println("SBuilder:" + sw.elapsedTime(TimeUnit.MILLISECONDS));
    }

The implmentation from my idea:

@Test
    public void insertWithRepeatString() {
        final int n = 100000;
        final String one = "MonkeyPony";
        final String two = "Monkey";

        final Stopwatch sw = new Stopwatch();
        int x = 1;
        for (; x <= 5; x++) { // loop 4 times (warming up) to avoid JIT
            System.out.println("warming up times:" + x);
            if (x == 5) {
                sw.start();
            }
            final StringBuilder builder = new StringBuilder(one);
            final int m = two.length() / 2;
            final String h1 = two.substring(0, m); //get Mon
            final String r1 = two.substring(m);    //get Key
            final String head = new String(new char[n - 1]).replace("\0", h1); //build repeat string
            final String tail = new String(new char[n - 1]).replace("\0", r1); //build repeat String
            final StringBuilder builder2 = new StringBuilder(head);
            builder2.append(two).append(tail);
            builder.insert(builder.length() / 2, builder2);
            if (x == 5) {
                sw.stop();
                // System.out.println("builder:" + builder.toString());
            }
        }
        System.out.println("Idea:" + sw.elapsedTime(TimeUnit.MILLISECONDS));
    }

The output:

warming up times:1
warming up times:2
warming up times:3
warming up times:4
warming up times:5
Idea:41
warming up times:1
warming up times:2
warming up times:3
warming up times:4
warming up times:5
SBuilder:4413 

Answer 4

This solution may be simple, but it'll consume enormous amount of time while comparring with others.
substring method has been utilized here.

import java.util.Scanner;

public class test {

     public static void main(String[] args) {

         int n=0;
         String str1,str2=null;


         Scanner in = new Scanner(System.in);

         System.out.println("Enter the String1.!");
         str1=in.nextLine();

         System.out.println("Enter the String2.!");
         str2=in.nextLine();

         System.out.println("Enter the Count.!"); 
         n=Integer.parseInt(in.nextLine());

         in.close();

         for(int i=0;i<n;i++)
         {
             //Concept: Say str1=TEST str2=123, Now the below code will do this TE + 123 + ST 
             str1=str1.substring(0,str1.length()/2) + str2 + str1.substring(str1.length()/2);
             System.out.println(str1);
         }


        }


}