Difference between concat and append in Java

Difference between concat and append in java:


  • String has concat method, remember string is immutable.
  • It adds a string to another string.
  • It will create the new object after concatenation done, since it is a immutable.


  • StringBuilder and StringBuffer has append method, remember these two are mutable.
  • It appends a char or char sequence to a string.
  • It will not create a new object, since it is a mutable one.

Example Program:

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package com.javadomain.in;

public class StringConcatenation {

public static void main(String[] args) {
//Concatenating string with another string
String helloVariable = "hello ";
String worldVariable = "world";
System.out.println(helloVariable.concat(worldVariable)); //hello world

//Appending string to string
StringBuilder helloStrBuilderVariable = new StringBuilder("hello");
StringBuilder worldStrBuilderVariable = new StringBuilder(" world");
System.out.println(helloStrBuilderVariable.append(worldStrBuilderVariable)); //prints hello world

//Appending char to string
StringBuilder charVariable = new StringBuilder("Java");
System.out.println(charVariable.append('D')); // prints JavaD



hello world
hello world




Must Know Differences in Java:

String vs StringBuilder vs StringBuffer Difference

Difference between equals() and == ?

Hashset vs LinkedHashSet vs TreeSet Difference

Difference between HashMap vs LinkedHashMap

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