half-payramid-pattern-1-12-123-1234.java

public class Main{
    public static void main(String[]args){
        
        for(int i=1; i<=4; i++){
            
            for(int j=1; j<=i; j++){
                
                System.out.print(j);
            }
            
            System.out.println();
            
        }
    }
}