Formula:
Area of Triangle = 1/2*base*height

 Method 1: Simple program
public class TriangleArea1{
    public static void main (String[] args){
        
        double base = 203;
        double height = 137;
        
        System.out.println ("First number: "+base);
        System.out.println ("Second number: "+height);
        
        double area = (base * height) / 2;
        
        System.out.println ("Area of "+base+" and "+height+" is: "+area);
    }

}

 Save this file as 'TriangleArea1.java'
Compile: $javac TriangleArea1.java
Execute: $java TriangleArea1
Output:

 First number: 203.0
Second number: 137.0

Area of 203.0 and 137.0 is: 13905.5

 Method 2: Using Object and Class
class Triangle1{
    
    //creating method
    public void m1(){
        double base = 320;
        double height = 115;
        
        System.out.println ("First number: "+base);
        System.out.println ("Second number: "+height);
        
        double area = (base * height) / 2;
        
        System.out.println ("Area of "+base+" and "+height+" is: "+area);
    }
}

 public class TriangleArea2{
    public static void main (String[] args){
        
        //creating new object
        Triangle1 r = new Triangle1();
        
        //calling method
        r.m1();
    }

}

Save this file as 'TriangleArea2.java'
Compile: $javac TriangleArea2.java
Execute: $java TriangleArea2
Output:

First number: 320.0
Second number: 115.0
Area of 320.0 and 115.0 is: 18400.0