Java Program to Illustrate String Interpolation

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String interpolation is a concatenation technique used to display output text dynamically or effectively by replacing the placeholder characters with variables (or strings in the subsequent examples).

It restructures the code and prevents the need to repeatedly use variables to produce the output. It makes it efficient to write lengthy variable names or text just by replacing the placeholder with the variable names allocated to strings.

String Interpolation in Java

There are several ways in Java to perform String Interpolation with the help of the concatenation operator and library function or class. Here, we will discuss four different methods of String Interpolation −

• By means of the '+' operator

• By means of the format () method

• By means of MessageFormat class

• By means of StringBuilder Class

Using the '+' operator

In the statement outside of the double quote marks, we can operate with strings by using the + operator. Depending on the circumstance or context, the variable or string name should come either before or after the + operator. We achieve interpolation or concatenation of texts by replacing the variable with its value.

Example

The following program is written to demonstrate the usage of String Interpolation using the + operator.

// Java Program to Illustrate String Interpolation 
import java.io.*;
public class StringInterpolation1 {
   // Main method
   public static void main(String[] args){
      // String 1
      String str1 = "Let us make the world";
      // String 2
      String str2 = " to live ";
      // String 3
      String str3 = " in. ";
      // display the Interpolated string
      System.out.println(
      str1 + " a better place "
      + str2 + str3);
   }
}

When you execute this code, it will show the below result −

Let us make the world a better place  to live  in.

Using the format() method

This approach keeps the text compact and simple to use for short sentences or expressions by separating the content from the expression and variable name. As the format() method receives the string as the first parameter and the variables as the second, the placeholders (%s for string) are utilized sequentially to fit in the values of the variables provided after the expression. Hence, there will be one more argument than there are string placeholders.

Example

The following program is written to demonstrate the usage of String Interpolation using the format() method.

// Java Program to Illustrate the working of String Interpolation
// by the means of the format () method
public class StringInterpolation2 {
      public static void main(String[] args){
      // String 1
      String str1 = "Let us make the world";
      // String 2
      String str2 = "to live ";
      // display the interpolated string
      System.out.println(String.format("%s a better place  %s in.", str1,str2));
   }
}

Following is the output of above code −

Let us make the world a better place  to live  in.

Using the MessageFormat Class

To use the MessageFormat class, which provides the format() method, we must import it. Apart from how the placeholders are written, the format() method in the MessageFormat class and the format() method in the String class are nearly similar.

However, the format() method of MessageFormat class prevent the repetitive use of the same variable. The placeholder is written using indexes like "0," "1," "2" and so on. This can have some positive advantages over the format() method in the string class.

Example

The following program is written to demonstrate String Interpolation using MessageFormat class

// java program to illustrate string interpolation 
//by the means of MessageFormat class
import java.io.*;
// Import MessageFormat class from the java.text package
import java.text.MessageFormat;
public class StringInterpolation2 {
   // Main method
   public static void main(String[] args) {
      // assigning value in String 1
      String str1 = "Have";
      // String 2
      String str2 = " working hard ";
      // String 3
      String str3 = "will";
      // String 4
      String str4 = "into";
      // display the interpolated string
      System.out.println(MessageFormat.format("{0} faith, keep {1} everything {2} fall {3} line.",	str1, str2, str3, str4));
   }
}

On running this code, it will display the below output −

Have faith, keep  working hard  everything will fall into line.

Using the StringBuilder Class

Due to its length and low usage, this strategy is relatively uncommon. We create a new object using the StringBuilder class, then we use the append() method to add the variable before the prepared text. This class allows for the chaining of as many append procedures as necessary. Yet, it makes the code difficult to read.

Example

The following program is written to demonstrate the usage of String Interpolation using the StringBuilder class.

// Java Program to illustrate String Interpolation
// by the means of StringBuilder class
import java.io.*;
public class StringInterpolation4 {
   public static void main(String[] args) {
      // String 1
      String str1 = "Tutorials Point ";
      // String 2
      String str2 = "is a website that";
      // String 3
      String str3 = "in technical as well as non technical domain";
      //display the interpolated string through
      //StringBuilder class and append() method
      System.out.println(
      new StringBuilder(str1)
      .append(str2)
      .append(" offers vast range of topics ")
      .append(str3)
      .append("."));
   }
}

On executing, this code will produce the following result −

Tutorials Point is a website that offers vast range of topics in technical as well as non technical domain.

Conclusion

This article demonstrate String Interpolation in Java. The article began with a discussion of the term String Interpolation. Further, four methods and their implementation were discussed to perform interpolation of the strings.