For-each loop in Java
Prerequisite: Decision making in Java
For-each is another array traversing technique like for loop, while loop, do-while loop introduced in Java5.
- It starts with the keyword for like a normal for-loop.
- Instead of declaring and initializing a loop counter variable, you declare a variable that is the same type as the base type of the array, followed by a colon, which is then followed by the array name.
- In the loop body, you can use the loop variable you created rather than using an indexed array element.
- It’s commonly used to iterate over an array or a Collections class (eg, ArrayList)
Syntax:
for (type var : array) { statements using var; }
is equivalent to:
for (int i=0; i<arr.length; i++) { type var = arr[i]; statements using var; }
// Java program to illustrate // for-each loop class For_Each { public static void main(String[] arg) { { int [] marks = { 125 , 132 , 95 , 116 , 110 }; int highest_marks = maximum(marks); System.out.println( "The highest score is " + highest_marks); } } public static int maximum( int [] numbers) { int maxSoFar = numbers[ 0 ]; // for each loop for ( int num : numbers) { if (num > maxSoFar) { maxSoFar = num; } } return maxSoFar; } } |
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Output:
The highest score is 132
Limitations of for-each loop
- For-each loops are not appropriate when you want to modify the array:
for (int num : marks) { // only changes num, not the array element num = num*2; }
- For-each loops do not keep track of index. So we can not obtain array index using For-Each loop
for (int num : numbers) { if (num == target) { return ???; // do not know the index of num } }
- For-each only iterates forward over the array in single steps
// cannot be converted to a for-each loop for (int i=numbers.length-1; i>0; i--) { System.out.println(numbers[i]); }
- For-each cannot process two decision making statements at once
// cannot be easily converted to a for-each loop for (int i=0; i<numbers.length; i++) { if (numbers[i] == arr[i]) { ... } }
Related Articles:
For-each in C++ vs Java
Iterator vs For-each in Java
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