How to append a string in Java  



Java

This tutorial will help you understand how to append a string in Java using different methods and string concatenation with examples.

String concatenation means appending two or more strings together to form a single string. The term append denotes to include an extra string to the existing string variable.

For example, a string contains the text “Welcome”. You have another string “Java”. When we want both strings together as a single string, we can append or concatenate both the strings to a single string.

Exanple:
String1 = "Welcome"
String2  = "Java"
Output: "Welcome Java"

How to append a string in JavaPin

Different ways to append a string  

There are different ways to concatenate or append a string in Java:

  • Using + operator
  • concat() method
  • append() method

String concatenation in JavaPin

Using + operator  

This is the simplest way to append a string. We can use the ‘+’ operator to concatenate two or more strings. The below example shows you how to append a string in Java using the + operator.

public class StringConcat {

  public static void main(String[] args) {
    String s1 = "Hello,";
    String s2 = "how are you";
    String s3 = s1 + s2;
    System.out.println("String 1: " + s1);
    System.out.println("String 2: " + s2);
    System.out.println("Concatenated string: " + s3);
    
  }

}
String 1: Hello,
String 2: how are you
Concatenated string: Hello,how are you

This method internally uses the append() method of the StringBuilder class. We will see this in detail towards the end.

String s = (new StringBuilder()).append("Hello,").append("how are you").toString();

We can append even primitive values along with string values using the ‘+’ operator.

System.out.println("Welcome Java" + 2020);
Welcome Java2020

String.concat() method  

Another way is to use the concat() method of the String class to append a string in Java. The below example shows you how to append a string in Java using the concat() method.

public class StringConcat {

  public static void main(String[] args) {
    String s1 = "Hello,";
    String s2 = "how are you";
    
    String s3 = s1.concat(s2);
    System.out.println("String 1: " + s1);
    System.out.println("String 2: " + s2);
    System.out.println("Concatenated string: " + s3);
    
  }

}
String 1: Hello,
String 2: how are you
Concatenated string: Hello,how are you

StringBuilder append() method  

The StringBuilder class has an append() method that accepts different types of parameters as in the below table.

See also
ReadWriteLock in Java
MethodDescription
append(boolean b)Appends a boolean parameter. Either true or false
append(char c)Appends a single character
append(char[] ch)Appends an array of characters
append(CharSequence s)Appends a character sequence
append(double d)Appends a double value parameter
append(float f)Appends a float value parameter
append(int i)Appends an integer value parameter
append(long l)Appends a long value parameter
append(Object o)Appends an object representation as parameter
append(String s)Appends a string value parameter
append(StringBuffer sb)Appends the StringBuffer as parameter
append(char[] ch, int offset, int len)Appends the subarray of the character array starting from the specified offset for the required length
append(CharSequence cs, int start, int end)Appends the specified character sequence based on the specified start and end parameter

append(boolean b)

The below code appends a boolean value to the current string in Java.

public class StringAppend {

  public static void main(String[] args) {
    Boolean b = true;
    StringBuilder sb = new StringBuilder("Java");
    sb.append(b);
    System.out.println(sb);

  }

}
Javatrue

append(char c)

The below code appends a character to the input string.

public class StringAppend {

  public static void main(String[] args) {
    char c = 'A';

    StringBuilder sb = new StringBuilder("Java");
    sb.append(c);
    
    System.out.println(sb);
  }

}
JavaA

append(char[] ch)

The below code appends an array of characters to the current string.

public class StringAppend {

  public static void main(String[] args) {
    
    char[] ch = {'J','A','V','A'};
    StringBuilder sb = new StringBuilder("Java");
    
    sb.append(ch);
    System.out.println(sb);
  }

}
JavaJAVA

append(char[] ch, int offset, int len)

The below code appends a specific character array length to the current string.

public class StringAppend {

  public static void main(String[] args) {
    
    char[] ch = {'L','A','N','G','U','A','G','E'};
    StringBuilder sb = new StringBuilder("Java");
    
    sb.append(ch, 0, 4);
    System.out.println(sb);
  }

}
JavaLANG

append(double d)

The below code appends a double value to the current string.

public class StringAppend {

  public static void main(String[] args) {
    
    double d = 54.56;
    
    StringBuilder sb = new StringBuilder("Java");
    
    sb.append(d);
    System.out.println(sb);
  }

}
Java54.56

append(float f)

The below code appends a float value to the current string.

public class StringAppend {

  public static void main(String[] args) {
    
    float f = 224.65f;
    
    StringBuilder sb = new StringBuilder("Java");
    
    sb.append(f);
    System.out.println(sb);
  }

}
Java224.65

append(int i)

Below is a program to append an integer value to the current string.

public class StringAppend {

  public static void main(String[] args) {
    
    int i = 100;
    
    StringBuilder sb = new StringBuilder("Java");
    
    sb.append(i);
    System.out.println(sb);
  }

}
Java100

append(String s)

The below code shows how to append a string to the input string in Java.

public class StringAppend {

  public static void main(String[] args) {
    
    String s = "Programming";
    StringBuilder sb = new StringBuilder("Java");
    
    sb.append(s);
    System.out.println(sb);
  }

}
JavaProgramming

Reference

Concatenation of two strings

Substring With Concatenation Of All Words

1