返回数组方法

Question

I am unclear as to what this is asking me to do, and how I execute it, in reference to the int [] copyAndReplaceLessThan(int []a, int b) method. Any help would be greatly appreciated, thanks.

Task:

Test this method in main. Print both the original array and the returned array which the method, copyAndReplaceLessThan, returns. Since this method returns a value (an integer array), you need to “catch” the returned value in a local variable (of type int []) in the calling method (main).

For example: Assuming you pass the array “x” to the method and use array “y” to catch the returned value. Print x before you call the method and then print both x and y after calling the method.

 public class ArrayExamples{
  public static void swapInts(int a, int b){  
    int temp;
    temp = a;
    a = b;
    b = temp;
}
public static void swapIntArrays(int [] a, int [] b){

   int x;
   for (int i=0; i<a.length; i++){
   x = a[i];
   a[i]=b[i];
   b[i]=x;

}
}
public static void printArray(int[] a){
   for(int i = 0; i < a.length; i++)
   {
    System.out.print(a[i] + " ");
   }
   System.out.println("");

}

public static void main(String args[]){

   int [] one ={3,4};
   int [] two ={7,8};
   printArray(one);
   printArray(two);
   swapIntArrays(one,two);
   printArray(one);
   printArray(two);
   System.out.println();

   int [] x ={3,45,17,2,-1,44,9,23,67,2,-6,-23,-100,12,5,1212};
   int b = 12;
   printArray(x);
   replaceLessThan(x,b);
   printArray(x);


   printArray(x);
   copyAndReplaceLessThan(x,b);
   printArray(x);
   printArray(y);


}

public static void replaceLessThan(int []a, int b){ 
  for(int i=0; i < a.length; i++){
    if(a[i] < b){
       a[i] = b;
    }
    else{
       a[i] = a[i];
    }
   }
}
public static int[] copyAndReplaceLessThan(int []a, int b){
  int []x = a;
  int[]y = x;

  for(int i=0; i < a.length; i++){
    if(a[i] < b){
      a[i] = b;
      y[i] = b;
    }
    else{
      a[i] = a[i];
      y[i] = a[i];
    }
    }
return y;
}
}

Answer 1

Some problems:

You're supposed to leave the original array unaltered, yet you're setting its elements with

a[i] = b;

And there's no point to doing this

a[i] = a[i];

as you're just resetting the value to itself.

But your biggest problem is that you're not creating a new array, as you're supposed to. Instead, your "new" array ( y ) is referring to the original one ( a ), and therefore any changes to y are actually being made in the original.

I also recommend that you either test or try a for null ness.

Answer 2

public static int[] copyAndReplaceLessThan(int[] a, int b)
{
    int[] x = a.clone();

    for (int i = 0; i < x.length; i++)
    {
        if (x[i] < b)
        {
            x[i] = b;
        }
    }
    return x;
}