// You're looking at a file named Class1.java,
      // which defines a class named Class1 that implements
      // the interface named Interface1.
      //
      // Ordinarily, we would write a purpose statement
      // for each field and for each method, but we're leaving
      // them out to emphasize the simplicity of Java class
      // definitions.
      //
      //
      //
      //
      //
      //
      //
      //
      //
      //
      //
      //
      
      class Class1 implements Interface1 {
      
          int x;
          int y;
          int r;
      
      
      
          // A JAVA CONSTRUCTOR GOES HERE
      
      
      
      
      
          // These are the method definitions.
      
          public int foo () {
              return x + y;
          }
      
          public int bar (int n) {
              return r + n;
          }
      
          public int baz (int n) {
              return this.bar(n) + n;
          }
      }

Although the class definition shown above will compile without errors, it is incomplete because we have omitted the Java constructor that will initialize the fields of objects of this class.