Java Menu Driven Program to Perform Basic String Operations

String refers to a sequence of characters. In Java Strings are objects. To create and manipulate strings Java provides the String class. String class has many inbuilt methods which are used for different purposes.

We will perform a few basic string operations by using inbuilt String methods.

replace() Method: It replaces a specified character in the given string.
concat() Method: It appends another string to the end of one string.
length() Method: It returns the length of the given String.
Equals() Method: It checks whether two strings are equal or not.

In this article, we will see some basic string operations like Joining two strings, Counting length of the string, comparing two strings using Java programming language. We will be implementing the application using a switch case.

To show you some instances ?

Instance-1

Suppose the first String is ?Java? and the second String is ?Python? then by joining two String will give ?JavaPython?. Here the concat() method will be used.

Instance-2

Suppose the first String is ?Java? and the second String is ?Python? then by counting two String will give its respective length as 4 and 6. Here length() method will be used.

Instance-3

Suppose the first String is ?Java? and the second String is ?Python? then by comparing two String will give "Both strings are not equal". Here equals() method will be used.

Instance-4

Suppose String is ?Java? and replace the letter ?J? with ?R? then the new string will be Rava. Here replace() method will be used.

Syntax

To perform basic string operations like joining the string, getting length of the string, comparing the string and replacing a specific value in a String we use concat(), length(), equals() and replace() methods respectively. The concat() method appends (concatenate) a string to the end of another string. The length() method returns the length of a specified string. The length of an empty string is 0. The equals() method compares two strings, and returns true if the strings are equal, and false if not. The replace() method replaces a specified value in a String with another new value.

Following is the syntax for "for loop" ?

for (statement 1; statement 2; statement 3) {
   // code block to be executed
}

Following is the syntax for concat function

string1.concat(string2)

Following is the syntax for length function

string1.length() 

Following is the syntax for equals function

string1.equals(string2)

Following is the syntax for replace function

string1.replace(?OldValue?, ?NewValue?)

Algorithm

Step-1 ? Declare a String variable and initialize the value.

Step-2 ? Display the menu.

Step-3 ? Ask the user to enter their choice.

Step-4 ? Use a switch case to go to the choice and perform the operation.

Step-5 ? Print the result.

Let?s see the program to understand it clearly.

Example

<div class="code-mirror  language-java" contenteditable="plaintext-only" spellcheck="false" style="outline: none; overflow-wrap: break-word; overflow-y: auto; white-space: pre-wrap;"><span class="token keyword">import</span> <span class="token namespace">java<span class="token punctuation">.</span>util<span class="token punctuation">.</span></span><span class="token operator">*</span><span class="token punctuation">;</span>
<span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">Main</span><span class="token punctuation">{</span>
   <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token class-name">String</span> args<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
      <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"First String"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
      <span class="token class-name">String</span> s1 <span class="token operator">=</span> <span class="token string">"Hello"</span><span class="token punctuation">;</span>
      <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"Second String"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
      <span class="token class-name">String</span> s2 <span class="token operator">=</span> <span class="token string">"World"</span><span class="token punctuation">;</span>
      mainLoop<span class="token operator">:</span> <span class="token keyword">while</span> <span class="token punctuation">(</span><span class="token boolean">true</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
         <span class="token class-name">Scanner</span> inn <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Scanner</span><span class="token punctuation">(</span> <span class="token class-name">System</span><span class="token punctuation">.</span>in <span class="token punctuation">)</span><span class="token punctuation">;</span>
         <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"\n***Menu***"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
         <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"1. Join Two Strings"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
         <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"2. Get length of a String"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
         <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"3. Compare two Strings"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
         <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"4. Replace a value in String"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
         <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"5. Terminate the program"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
         <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"Enter action number (1-5): "</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
         <span class="token keyword">int</span> command<span class="token punctuation">;</span>
         <span class="token keyword">if</span> <span class="token punctuation">(</span>inn<span class="token punctuation">.</span><span class="token function">hasNextInt</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
            command <span class="token operator">=</span> inn<span class="token punctuation">.</span><span class="token function">nextInt</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
            inn<span class="token punctuation">.</span><span class="token function">nextLine</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
         <span class="token punctuation">}</span>
         <span class="token keyword">else</span><span class="token punctuation">{</span>
            <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"\nILLEGAL RESPONSE. YOU MUST ENTER A NUMBER."</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
            inn<span class="token punctuation">.</span><span class="token function">nextLine</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
            <span class="token keyword">continue</span><span class="token punctuation">;</span>
         <span class="token punctuation">}</span>
         <span class="token keyword">switch</span><span class="token punctuation">(</span>command<span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token keyword">case</span> <span class="token number">1</span><span class="token operator">:</span>
               <span class="token class-name">String</span> joinedString <span class="token operator">=</span> s1<span class="token punctuation">.</span><span class="token function">concat</span><span class="token punctuation">(</span>s2<span class="token punctuation">)</span><span class="token punctuation">;</span>
               <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"Joined String: "</span> <span class="token operator">+</span> joinedString<span class="token punctuation">)</span><span class="token punctuation">;</span>
               <span class="token keyword">break</span><span class="token punctuation">;</span>
            <span class="token keyword">case</span> <span class="token number">2</span><span class="token operator">:</span>
               <span class="token keyword">int</span> length1 <span class="token operator">=</span> s1<span class="token punctuation">.</span><span class="token function">length</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
               <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"Length of first String: "</span> <span class="token operator">+</span> length1<span class="token punctuation">)</span><span class="token punctuation">;</span>
               <span class="token keyword">int</span> length2 <span class="token operator">=</span> s2<span class="token punctuation">.</span><span class="token function">length</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
               <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"Length of second String: "</span> <span class="token operator">+</span> length2<span class="token punctuation">)</span><span class="token punctuation">;</span>
               <span class="token keyword">break</span><span class="token punctuation">;</span>
            <span class="token keyword">case</span> <span class="token number">3</span><span class="token operator">:</span>
               <span class="token keyword">boolean</span> result <span class="token operator">=</span> s1<span class="token punctuation">.</span><span class="token function">equals</span><span class="token punctuation">(</span>s2<span class="token punctuation">)</span><span class="token punctuation">;</span>
            <span class="token keyword">if</span><span class="token punctuation">(</span>result <span class="token operator">==</span> <span class="token boolean">true</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
               <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"Strings first and second are equal"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
            <span class="token punctuation">}</span>
            <span class="token keyword">else</span><span class="token punctuation">{</span>
               <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"Strings first and second are not equal"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
            <span class="token punctuation">}</span>
            <span class="token keyword">break</span><span class="token punctuation">;</span>
            <span class="token keyword">case</span> <span class="token number">4</span><span class="token operator">:</span>
               <span class="token class-name">String</span> newString <span class="token operator">=</span> s2<span class="token punctuation">.</span><span class="token function">replace</span><span class="token punctuation">(</span><span class="token string">'W'</span><span class="token punctuation">,</span> <span class="token string">'Z'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
               <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"After replacing the new string is: "</span><span class="token operator">+</span>newString<span class="token punctuation">)</span><span class="token punctuation">;</span>
               <span class="token keyword">break</span><span class="token punctuation">;</span>
            <span class="token keyword">case</span> <span class="token number">5</span><span class="token operator">:</span>
               <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"Program terminated"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
               <span class="token keyword">break</span> mainLoop<span class="token punctuation">;</span>
            <span class="token keyword">default</span><span class="token operator">:</span>
               <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"Wrong choice!!"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

         <span class="token punctuation">}</span>
      <span class="token punctuation">}</span>
   <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</div>

Output

First String
Second String

***Menu***
1. Join Two Strings
2. Get length of a String
3. Compare two Strings
4. Replace a value in String
5. Terminate the program
Enter action number (1-5):
2
Length of first String: 5
Length of second String: 5

***Menu***
1. Join Two Strings
2. Get length of a String
3. Compare two Strings
4. Replace a value in String
5. Terminate the program
Enter action number (1-5):
1
Joined String: HelloWorld

***Menu***
1. Join Two Strings
2. Get length of a String
3. Compare two Strings
4. Replace a value in String
5. Terminate the program
Enter action number (1-5):
4
After replacing the new string is: Zorld

***Menu***
1. Join Two Strings
2. Get length of a String
3. Compare two Strings
4. Replace a value in String
5. Terminate the program
Enter action number (1-5):
3
Strings first and second are not equal

***Menu***
1. Join Two Strings
2. Get length of a String
3. Compare two Strings
4. Replace a value in String
5. Terminate the program
Enter action number (1-5):
5
Program terminated

In this article, we explored how to perform simple string operations in Java by using menu driven approach.