java achieve print diamond hollow diamond triangle

public class LingXing {
public static void main(String[] args) {


Scanner sc = new Scanner(System.in);


System.out.println("请输入行数:");


int num = sc.nextInt();


for (int i = 0; i <= num; i++) {
for (int j = 0; j < num - i; j++) {
System.out.print(" ");
}
for (int k = 1; k <= 2 * i - 1; k++) {
System.out.print("*");
}


System.out.println();
}


for (int i = num - 1; i > 0; i--) {
for (int j = 0; j < num - i; j++) {
System.out.print(" ");
}
for (int k = 1; k <= 2 * i - 1; k++) {
System.out.print("*");
}


System.out.println();
}


}

}

Open diamonds:

public class LingXing {
public static void main(String[] args) {


Scanner sc = new Scanner(System.in);


System.out.println("请输入行数:");


int num = sc.nextInt();


for (int i = 0; i <= num; i++) {
for (int j = 0; j < num - i; j++) {
System.out.print(" ");
}
for (int k = 1; k <= 2 * i - 1; k++) {
if (k == 1 || k == 2 * i - 1) {
System.out.print("*");
} else {
System.out.print(" ");
}
}


System.out.println();
}


for (int i = num - 1; i > 0; i--) {
for (int j = 0; j < num - i; j++) {
System.out.print(" ");
}
for (int k = 1; k <= 2 * i - 1; k++) {
if (k == 1 || k == 2 * i - 1) {
System.out.print("*");
} else {
System.out.print(" ");
}
}


System.out.println();
}


}
}

Triangle is to knock out the top half of the diamond on the line, do not understand, please leave a message!