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javafor-loop
Nick Heiner
Nick Heiner

Reputation: 122412

Java: Initialize multiple variables in for loop init?

I want to have two loop variables of different types. Is there any way to make this work?

@Override
public T get(int index) throws IndexOutOfBoundsException {
    // syntax error on first 'int'
    for (Node<T> current = first, int currentIndex; current != null; 
            current = current.next, currentIndex++) {
        if (currentIndex == index) {
            return current.datum;
        }
    }
    throw new IndexOutOfBoundsException();
}

Upvotes: 108

Views: 113220

Answers (4)

Vishnu Prasanth Gangisetty
Vishnu Prasanth Gangisetty

Reputation: 1233

Variables declared in the initialization block must be of same type

we can't initialize the different data types in the for loop as per their design. I'm just putting a small example.

for(int i=0, b=0, c=0, d=0....;/*condition to be applied */;/*increment or other logic*/){
      //Your Code goes here
}

Upvotes: 6

McDowell
McDowell

Reputation: 108859

The initialization of a for statement follows the rules for local variable declarations.

This would be legal (if silly):

for (int a = 0, b[] = { 1 }, c[][] = { { 1 }, { 2 } }; a < 10; a++) {
  // something
}

But trying to declare the distinct Node and int types as you want is not legal for local variable declarations.

You can limit the scope of additional variables within methods by using a block like this:

{
  int n = 0;
  for (Object o = new Object();/* expr */;/* expr */) {
    // do something
  }
}

This ensures that you don't accidentally reuse the variable elsewhere in the method.

Upvotes: 122

Nikita Rybak
Nikita Rybak

Reputation: 68006

Just move variable declarations (Node<T> current, int currentIndex) outside the loop and it should work. Something like this

int currentIndex;
Node<T> current;
for (current = first; current != null; current = current.next, currentIndex++) {

or maybe even

int currentIndex;
for (Node<T> current = first; current != null; current = current.next, currentIndex++) {

Upvotes: 12

Colin Hebert
Colin Hebert

Reputation: 93157

You can't like this. Either you use multiple variables of the same type for(Object var1 = null, var2 = null; ...) or you extract the other variable and declare it before the for loop.

Upvotes: 24

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