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unable to understand the output

 
nishant vats
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int[] a = new int[2];
int n =0;
a[++n]= ++n;


System.out.println("the array contains "+ a[0] +a[1]);

output 0 2

can u explain what is logic behind output and if i change it to
a[n++]=++n;
then output is
output 2 0
 
Andris Jekabsons
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In the first example "a[ ++n ]" the increment is performed BEFORE evaluating the value of n.
So, the expressions becomes "a[ 0+1 ] = ++n", that is: "a[ 1 ] = ++n".
n now has value of 1, and it is incremented on the left side of " = ":
"a[ 1 ] = 1+1", that is: "a[ 1 ] = 2"
a[ 0 ] remains with the default value of 0.

In the second example "a[ ++n ]" the increment is performed AFTER evaluating the value of n.
So, the expressions becomes "a[ 0 ] = ++n".
Only then n is assigned the value of 1, and it is incremented on the left side of " = ":
"a[ 0 ] = 1+1", that is: "a[ 0 ] = 2"
a[ 1 ] remains with the default value of 0.
 
nishant vats
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thanks for reply but i guess in assignment operator right hand evaluation is done before ..in that case ++n is evaluated first.. so can u nw explain the answer
 
Joe Sondow
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nish vats, that seems like a reasonable assumption but it turns out to be incorrect. The left-hand operand is evaluated first in order to determine the variable that will receive the newly assigned value. The entire procedure is described in the JLS 15.26.1.
 
nishant vats
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thanks joe ...
 
Consider Paul's rocket mass heater.
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