Triangle & Right Triangle

I have a Triangle class

public class Triangle {

	private int side1, side2, side3;
	
	
	public Triangle(){
		
		side1 = 3;
		side2 = 4;
		side3 = 5;
		
	}
	
	public Triangle(int a, int b, int c){
		
		this();
		setSide1(a );
		setSide2(b );
		setSide3(c );
		
	}
	
	public void setSide1 (int a){
		
		if ( a > 0)
			
			side1 = a;
		
	}
	
	public void setSide2 (int b ){
		
		if ( b > 0)
			
			side2 = b;
		
	}
	
	public void setSide3 (int c){
	
		if ( c > 0)
		
			side3 = c;
	
	}
	

	
	public int getSide1() {
		
		return side1;
		
	}
	
	public int getSide2(){
		
		return side2;
		
	}
	
	public int getSide3(){
		
		return side3;
		
	}
	
	public String toString( ) {
		
		return "[ " + side1 + ", " + side2 + ", " + side3 + " ]" ;
		
	}
	
	public int findPerimeter ( ) {
		
		return side1 + side2 + side3;
		
	}
}

and here is the RightTriangle class which Extends Triangle

public class RightTriangle extends Triangle {
	
	private int side1, side2, side3;

	public RightTriangle() {
		
		super();
		
	}
	
	
	public RightTriangle ( int a, int b , int c){
		
		this();	
		
		if ( ((a* a) == (b * b ) + (c* c)) || ((b * b ) == (a * a) + (c * c)) || ((c * c) == (b * b ) + (a * a)) ){
			
			setSides( a, b , c );
		
		}	
	}
	
	public void setSides(int a, int b, int c){
	
		if( a > 0 && b > 0 && c > 0 ){
			
			side1 = a;
			side2 = b;
			side3 = c;	
					
		}	
	}
	
	public int getSide1() {
			
			return side1;
			
		}
		
		public int getSide2(){
			
			return side2;
			
		}
		
		public int getSide3(){
			
			return side3;
			
		}
	
	
}	
	

how can I prevent the inherited methods to not making the right triangle invalid?

in main I have these code:

public class RightTriangleApplication {
	
	public static void main( String args[] ){
		
		Triangle triangles[] = new Triangle [ 5 ];
		triangles [ 0 ] = new Triangle();
		triangles [ 1 ] = new RightTriangle();
		triangles [ 2 ] = new RightTriangle( 8, 15, 17 );
		triangles [ 3 ] = new Triangle( 5, 9, 12 );
		triangles [ 4 ] = new RightTriangle( 5, 9, 12 );
		
		for( Triangle t : triangles )
			
			System.out.println( t );
		
	}

}

and when I run the program I get the default side lengths which are [3 , 4, 5] that sets in the default constructor in Triangle class!

could you please help me to solve this problem?!