Java If statement practice

First question: finding the root of a two-second equation

public class Lianxi1 {

public static void main (string[] Args) {

System.out.println ("please Enter a value");
Scanner sc = new Scanner (system.in);
String A=sc.nextline ();
int x = Integer.parseint (a);
If (x!=0)
{
System.out.println ("please Enter the value of b");
Scanner SC1 =new Scanner (system.in);
System.out.println ("please Enter the value of c");
Scanner SC2 =new Scanner (system.in);
String B=sc1.nextline ();
String C=sc2.nextline ();
int y=integer.parseint (b), Z=integer.parseint (c), zhong=y*y-4*x*z;
Double i= (-y+math.sqrt (zhong))/(2*x), j= (-y+math.sqrt (zhong))/(2*x);

If (zhong<0) {
System.out.println ("the equation does not have a real root");
}
else if (zhong==0) {
System.out.println ("the equation has an identical real number root:" +i);
}
else{
System.out.println ("the equation has two distinct real roots:" +i+ "," +j ");
}
}

}

}

Second Question: enter a year to determine the horizontal leap years

public class Lianxi1 {

public static void main (string[] Args) {

System.out.println ("please Enter a year");
Scanner sc = new Scanner (system.in);
String a =sc.nextline ();
int X=integer.parseint (a);
If (x%400==0 | | x%4==0&&x%100!=0) {
System.out.println (a + "years is a leap year");
}
Else
{
System.out.println (a + "year is common year");
}
}

}

The third question: enter three number comparison size, output the largest number

public class Lianxi1 {

public static void main (string[] Args) {

System.out.println ("please enter");
Scanner sc = new Scanner (system.in);
String X=sc.nextline ();
String Y=sc.nextline ();
String Z=sc.nextline ();
Double a=double.parsedouble (x);
Double b=double.parsedouble (y);
Double c=double.parsedouble (z);
If (a>b) {
If (a>c) {
System.out.println (a);
}
Else
{
System.out.println (c);
}
}
Else
{
If (b>c) {
System.out.println (b);
}
Else
{
System.out.println (c);
}

}

}

}

Question Fourth: Enter gender, height, weight, figure

public class Lianxi1 {

public static void main (string[] Args) {

System.out.println ("please Enter your gender");
Scanner sc1=new Scanner (system.in);
String Sex=sc1.nextline ();
If (sex.equals ("male"))
{
System.out.println ("please Enter your height");
Scanner sc2=new Scanner (system.in);
String A=sc2.nextline ();

System.out.println ("please Enter your weight");
Scanner sc3=new Scanner (system.in);
String B=sc3.nextline ();
Double gao=double.parsedouble (a), zhong=double.parsedouble (b), bz=gao-100;
If (bz-zhong>=-3 && bz-zhong<=3) {
System.out.println ("you are the standard weight");
}
else if (bz-zhong<-3) {
System.out.println ("you are overweight");
}
else{
System.out.println ("you are thin");
}

}
else if (sex.equals ("female"))
{
System.out.println ("please Enter your height");
Scanner sc2=new Scanner (system.in);
String A=sc2.nextline ();

System.out.println ("please Enter your weight");
Scanner sc3=new Scanner (system.in);
String B=sc3.nextline ();
Double gao=double.parsedouble (a), zhong=double.parsedouble (b), bz=gao-110;
If (bz-zhong>=-3 && bz-zhong<=3) {
System.out.println ("you are the standard weight");
}
else if (bz-zhong<-3) {
System.out.println ("you are overweight");
}
else{
System.out.println ("you are thin");
}
}
Else
{
System.out.println ("are you a man or a Woman?") ");
}

}

}

Java If statement practice