java，for语句求奇数偶数的问题？

Question

public class tfor
{

public static void main (String []aegs){
    for (int a = 0; a <100;a++){
        if (a % 2 != 0);{

            System.out.println(a);
            a++;
        }
    }               
}

}
结果为偶数

public class tfor
{

public static void main (String []aegs){
    for (int a = 0; a <100;a++){
        if (a % 2 != 0);{
            a++;
            System.out.println(a);
        }
    }               
}

}
结果为奇数

public class tfor
{

public static void main (String []aegs){
    for (int a = 0; a <100;a++){
        if (a % 2 != 0);{

            System.out.println(a);
        }
    }               
}

}
结果为1~100

请问这段代码a++的位置不同导致结果不同，是为什么有大神能解释一下吗，笑答万分感谢

Answer 1

等价代码：

  for (int a = 0; a <100; ){
        {
            System.out.println(a);
            a=a+2;
        }
    }      

  for (int a = 0; a <100; ){
       {
            a=a+1;
            System.out.println(a);
            a=a+1;
        }
    }      

  for (int a = 0; a <100; ){
       {
            System.out.println(a);
            a=a+1;
        }
    }