java - Different looping behaviors in Groovy -

why these 2 loops have different results? thought both initialize of values in each array 5 second 1 works. explain why is?

static main(args) {     double[][] x = new double[3][3]     double[][] y = new double[3][3]      for(row in x)     {         for(num in row)         {             num=5         }     }      for(int i=0;i<y.size();i++)     {         for(int j=0;j<y[i].size();j++)         {             y[i][j]=5         }     }      println "x: ${x}"      println "y: ${y}" } 

and here's output

x: [[0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0]] y: [[5.0, 5.0, 5.0], [5.0, 5.0, 5.0], [5.0, 5.0, 5.0]] 

first pair of for loops nothing , correct. num new variable in scope of inner for. reference integer table. when assign it, becomes reference value 5. table cell not change.

for c programmer.

int 5 = 5; int *num; 

it is:

num = &five; 

it not:

*num = five;