for(int i = 1;i<=4;i++){
            for(int j = 4;j>=1;j--){
                if(j>i){
                    System.out.print(" ");
                }else{
                    System.out.print(i+1-j);
                }
            }
            for(int k = 1;k<i;k++){
                System.out.print(i-k);
            }
            System.out.println();
        }

------解决方案--------------------
Java code

public class OutputNum {
    public static void main(String[] args){
        int line = 4;//输出行数(可改变line来控制输出行数)
        int n, d;
        for(int i = 1; i <= line; ++i){
            n = 1;
            d = 1;
            for(int j = 0; j < line - i; ++j)
                System.out.print("  ");
            while(n > 0){
                System.out.print(n + " ");
                if(n == i)
                    d = -1;
                n += d;
            }
            System.out.println();
            
            
        }
    }
    

}


      1 
    1 2 1 
  1 2 3 2 1 
1 2 3 4 3 2 1

------解决方案--------------------
public class tezx {
	public static void main(String[] args) {
	     Scanner input=new Scanner(System.in);
	     System.out.println("请输入一个数");
	     int num=input.nextInt();
	     for(int i=1;i<=num;i++){
	    	 for(int j=1;j<=num-i;j++){
	    		 System.out.print(" ");
	    	 }
	    	 for(int j=1;j<=i;j++){
	    	   System.out.print(j);
	    	 }
	    	 if(i>1){
	    		for(int j=i-1;j>=1;j--){
	    			System.out.print(j);
	    		}
	    		 System.out.println();
	    	 }else{
	    		 System.out.println();
	    	 }
	    	
	     }
	}

}

------解决方案--------------------
for example
Java code
int n = 4;
for (int i=0; i<n; i++) {
    String format = "%" + String.format("%ds", 2*(n-i)-1);
    System.out.printf(format, " ");
    for (int j=1; j<2*(i+1); j++) {
        if (j <= i) {
            System.out.printf("%d ", j);
        } else {
            System.out.printf("%d ", 2*(i+1)-j);
        }
    }
    System.out.println();
}

------解决方案--------------------
Java code

public class TestPromt {

    public static void main(String arga[]) {

        int initNum = 5;

        for (int i = 1; i <= initNum; i++) {
            format(initNum ,i);
            generator(i);
        }

    }

    public static void generator(int i) {
        StringBuffer sb = new StringBuffer();
        String myString = "";
        for (int t = 1; t < i; t++) {
            sb.append(t).append(" ");
        }
        sb.append(i);
        myString = sb.toString();
        sb.reverse().delete(0,String.valueOf(i).length());
        System.out.println(myString + sb.toString());
    }
    public static void format(int initNum ,int i){
        for (int k = 2 * (initNum -i); k > 0; k--)
            System.out.print(" ");
    }

}

------解决方案--------------------
二维数组就可以了，很简单的