preincrement / postincrement in java

Question

Can someome help me to understand why:

int i=1;
int j=1;
int k=1;
int l=1;

System.out.println(i++ + i++);  
System.out.println(++j + ++j);  
System.out.pri         


        

Answer 1

Things to know:
1. Java evaluates expressions from left to right
2. ++i-pre-increment i.e increment before assignment
3. i++ - post increment i.e. increment after assignment

System.out.println(i++ + i++);

op1=i++
op2=1++
sum=op1+op2
i++ - post increment the value of i

1. Assign i to op1 and then increment the value of i.op1=1,i=2
2. Assign i to op2 and then increment the value of i.op2=2,i=3

3. Sum=3

   System.out.println(++j + ++j);

op1=++j
op2=++j
sum=op1+op2
++i - Pre increment the value of i

1. now at first j will be incremented to 2 and then assigned to op1.
2. Then, j will again be incremented to 3 and assigned to op2

3. Then, op1 and op2 will be added to print the sum as 5 and the value of j will be

   System.out.println(k++ + ++k);

op1=k++
op2=++k
sum=op1+op2

1. Assign the value of k to op1 and then increment k. op1=1,k=2

2. Increment the value of k and then assign to op2. op2=3,k=3

3. Sum = 4

   System.out.println(++l + l++);

Apply the above logic here also.