Check an array for equality

[ahmed yehia]

I have an array of int type, I want check that array to see if it has equal elements for example: {1,1,1,1,1} return true, otherwise false.
I have written this code, it works well but I want know if its good or there better algorithm.

 
public boolean testEqual(int[] array) {
int a = array[0];
for(int i = 1; i < array.length; i++) {
if(a != array[i])
break;
else {
a = array[i];
if(i == array.length -1)
return true;
}
}
return false;
}

[Scott Johnson]

See java.util.Arrays. It has some methods you'll be interested in.

[marc weber]

"Talt,"

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[Jesper de Jong]

Your code works, but looks unnecessarily complicated. You can do it in a more simple way like this:

public boolean testEqual(int[] array) {
    for (int i = 1; i < array.length; i++) {
        if (array[i] != array[0]) {
            return false;
        }
    }
 
    return true;
}

[ January 10, 2007: Message edited by: Jesper Young ]

[Peter Chase]

Originally posted by Scott Johnson:
See java.util.Arrays. It has some methods you'll be interested in.

It does have some good methods for working with arrays, but not one for testing if all elements are the same ... does it?

[Gary Edwards]

Originally posted by Peter Chase:


It does have some good methods for working with arrays, but not one for testing if all elements are the same ... does it?

You can always use Array's equals method:

int[] a = {1,2,3,4,5};
int[] b = {1,2,3,4};
int[] c = {1,2,3,4,5};
System.out.println("a=b: " + Arrays.equals(a, b));  // false
System.out.println("b=c: " + Arrays.equals(b, c));  // false
System.out.println("a=c: " + Arrays.equals(a, c));  // true

[ January 11, 2007: Message edited by: Gary Edwards ]

[Jim Yingst]

There appear to be two different ideas here about what is meant by "check an array for equality". Gary and (maybe) Scott are talking about checking if two different arrays are equal to each other, in the sense that the corresponding elements are equal. I.e. a[0] == b[0], a[1] == b[1], etc. But the original poster and others are talking about checking one array to see if all the elements are equal to each other. I.e. a[0] == a[1] == a[2] etc. These are completely different problems; let's not mix them up.

[Gary Edwards]

Oops...I really ought to learn how to read things a little more closely!

[ahmed yehia]

The orignal problem I have is to check a grid of elements
modeled as 2D array to see if 1 row or column has equal elements.
However checking 1D array seems different.

[Anton Uwe]

You could speed up the code a bit:

public boolean testEqual(int[] array) {
int a = array[0];
int i;
for( i = 1; i < array.length; i++) {
if(a != array[i]) break;
}
if(i == array.length )
return true;
else return false;
}