Foreach in C++ and JAVA

28 Aug 2024 | 4 min read

The foreach loop is used to quickly iterate over the elements of a container (array, vectors, etc.) without performing initialization, testing, or increment/decrement. Foreach loops work by doing something for each element rather than doing something n times. Although there is no foreach loop in C, it is supported by C++ and Java. It was first introduced in C++ in C++ 11, and in Java in JDK 1.5.0. In both C++ and Java, the keyword for foreach loop is "for."

Syntax

We no longer need to specify the data type for variables in foreach loops thanks to the introduction of the auto keyword in C++ and the var keyword in Java. Type inference detects the data type of the container and sets the variable used for traversing to the same data type.

The code below demonstrates the use of a foreach loop for various containers, as well as the auto/var keywords in C++/Java.

C++

JAVA

Output

Traversing the array with foreach using array's data type: 10 20 30 40 
Traversing the array with foreach using auto keyword     : 10 20 30 40

Vector C++ programme:

Output

Traversing the vector with foreach using vector's data type: This is foreach example using vector. 
Traversing the vector with foreach using auto keyword      : This is foreach example using vector.

C++/Java Set Program:

C++

JAVA

Output

Traversing the set with foreach using set's data type: 1 2 4 5 6 7 10 
Traversing the set with foreach using auto keyword   : 1 2 4 5 6 7 10

For array, vector, and set, we can use different data types in foreach.

C++/Java Map Program:

C++

JAVA

Output

Traversing the map with foreach using map's data type
1 Geeks
2 4
3 Geeks
4 Map
5 Foreach
6 Example

Traversing the map with foreach using auto keyword
1 Geeks
2 4
3 Geeks
4 Map
5 Foreach
6 Example

Foreach loop has the following advantages:

This improves the readability of the code.
Removes the possibility of data over- or under-running errors.

Foreach loop has the following disadvantage:

It is not possible to iterate over the elements in reverse order.
Every element will be accessed; no elements in between will be skipped.

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Foreach in C++ and JAVA

Syntax

C++

JAVA

Vector C++ programme:

C++/Java Set Program:

C++

JAVA

C++/Java Map Program:

C++

JAVA

Foreach loop has the following advantages:

Foreach loop has the following disadvantage:

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