Difference between concat and append in Java

Difference between concat and append in java:

In core java, its difficult to write a meaningful program without string data type. StringBuffer and StringBuilder’s are different variations of the String for different purpose in java.

But we as a java developer, needs to use concat() for string and append() for stringbuilder and stringbuffer.  Knowing the difference between these two makes us a good quality developer, as this will help us to use the best one at the right use cases.

concat():

• 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.

Concat() Java Sample Program:

package com.ngdeveloper;
public class StringConcat {
 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
 }
}

Concat() Java Sample Output:

hello world

append():

• 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.

append() Java sample Program:

package com.ngdeveloper;
public class StringBufferBuilderAppend {
 public static void main(String[] args) {
 //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("Ng");
 System.out.println(charVariable.append('Developer')); // prints JavaD
 }
}

append() Java Sample Output:

NgDeveloper

Difference between concat and append Java Program:

package com.ngdeveloper;
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
 }
}

Output:

hello world
hello world
JavaD

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String vs StringBuilder vs StringBuffer Difference

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Difference between HashMap vs LinkedHashMap