Differences between I ++ in java and I ++ in C

Differences between I ++ in java and I ++ in C

In java:

Using the intermediate variable mechanism:
I = I ++;

Equivalent:

Temp = I;
I = I + 1;
I = temp; (I = I ++ = temp)

# Note: An auto-increment command (I .e: before the "+" and "=" operations are executed, they are automatically added ). ##

Problem: in java, a temporary variable is allocated for each auto-increment operation when performing the auto-increment operation. If it is a prefix plus (++ I ), "First add 1 and then assign value (to the temporary variable)". If it is a suffix add (I ++), it will "assign value first (to the temporary variable) and then add 1 ". The final operation is not a variable, but a temporary variable assigned a value.

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Int a = 0, sum;

In java, after the expression a ++ is used, a immediately adds one;

For sum = a ++;

In java: after the first a ++ execution is complete, the value of a is immediately added to 1. Before the second a ++ execution, the value of a is 1.

A = 0;
A = a ++;

Temp1 = a; --> temp1 = 0;
A = a + 1;
Temp2 = a; --> temp2 = 1;
A = a + 1;
A = temp1 + temp2;

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Int a = 0, sum;

A = a ++;
System. out. println ();

Result: 0. Note: The process of changing the value of variable a is as follows: 0 --> 1 --> 0 (Initialization is 0 --> a auto-increment is 1 --> assign the value 1 of the temporary variable to)
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Int a = 0, sum;

Sum = a ++;

System. out. println (sum );
System. out. println ();

Result: 1 and 2

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Int a = 0, sum;

A = a ++;

System. out. println ();

Result: 1

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Int a, sum;
A = 0;

Sum = a ++;

System. out. println (sum );
System. out. println ();

Result: 2 and 2

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C language:

++ Is a unary operator: + and = are both binary operators.

For The unary operator, the return value is: I ++ is the value of I, and ++ I is the value after I plus.

The I ++ operation means that an auto-increment command is generated after the command corresponding to the binary operator is generated (that is, the auto-increment command is generated after the "+" and "=" operations are completed ).

The ++ I operation means that an auto-increment command is generated before the command corresponding to the binary operator is generated (that is, the auto-increment command is generated before the "+" and "=" operations are executed ).

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Int I = 0, sum;

// Test The unary operator

If printf ("% d", I); the result is: 0

If printf ("% d", I ++); the result is: 0

If printf ("% d", ++ I); the result is: 1

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Int I = 0, sum;

// Test the binary operator

Sum = I ++;

Printf ("% d", sum );
Printf ("% d", I );

Result: 0 and 1

If changed:

I = I ++;
Printf ("% d", I );

The result is: 1

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Int a = 0, sum;

Sum = a ++;

Printf ("% d \ n", sum );
Printf ("% d \ n", );

Result: 0 and 2

Analysis:

First execute the first a ++ (at this time, the value of a is 0 ),

Then execute the second a ++ (in this case, the value of a is 0 ),

Finally, perform addition and value assignment (in this case, the value of a is 0, and the value of sum is 0 + 0 = 0 ),

After the addition operation is complete, execute the two add-on action of a (the value of a is 2)

If changed:

A = a ++;

Printf ("% d", );

The result is: 2

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Int a = 0, sum;

A = a ++;
Printf ("% d \ n", );

Process:
First, a increases by 1, which is brought by ++ a (even if a ++ is on the far left ). At this time, a = 1

Then, we calculate the two operands of the plus sign.
Because they are actually all a (this involves the implementation of the compiler, most C compilers will merge these two operands, that is, all are variable ),
In this case, the return value of a ++ a is 1 + 1 = 2, and then the value of a ++ a is assigned to, at this time, a = 2

Finally, complete the auto-increment command brought by a ++. The value of a is 2 + 1 = 3, which is a = 3.

Result: 3

If changed:
Sum = a ++;
Printf ("% d", sum );
Printf ("% d", );

Process:
First, a increases by 1, which is brought by ++ a (even if a ++ is on the far left ). At this time, a = 1

Then, we calculate the two operands of the plus sign.
Because they are actually all a (this involves the implementation of the compiler, most C compilers will merge these two operands, that is, all are variable ),
In this case, the return value of a ++ a is 1 + 1 = 2, and then the value of a ++ a is assigned to sum, sum = 2, a = 1

Finally, complete the auto-increment command brought by a ++. At this time, the value of a is 1 + 1 = 2, which is a = 2.

Result: 2 and 2

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A = a ++ a; Difference between java and C

In java, execute a ++ first,
In C, execute ++ a first