8016576: Overrides warnings in jdi and jconsole

Summary: Implement hashCode() in classes emitting warnings
Reviewed-by: alanb, chegar

src/share/classes/com/sun/tools/jdi/SDE.java

@@ -171,7 +171,7 @@ class SDE {
         }
 
         public boolean equals(Object obj) {
-            if ((obj != null) && (obj instanceof LineStratum)) {
+            if (obj instanceof LineStratum) {
                 LineStratum other = (LineStratum)obj;
                 return (lti == other.lti) &&
                        (sti == other.sti) &&
@@ -182,6 +182,11 @@ class SDE {
             }
         }
 
+        @Override
+        public int hashCode() {
+            return (lineNumber() * 17) ^ refType.hashCode();
+        }
+
         int lineNumber() {
             return stiLineNumber(sti, lti, jplsLine);
         }

src/share/classes/sun/tools/jconsole/inspector/XObject.java

@@ -27,6 +27,7 @@ package sun.tools.jconsole.inspector;
 
 // java import
 import javax.swing.*;
+import java.util.Objects;
 
 /**
  * This provides a wrapper to the Object class to allow it to be
@@ -48,18 +49,17 @@ public class XObject extends JLabel {
     }
 
     public boolean equals(Object o) {
-        try {
-            if (o instanceof XObject) {
-                return object.equals(((XObject)o).getObject());
-            }
-        }
-        catch (Throwable t) {
-            System.out.println("Error comparing XObjects"+
-                               t.getMessage());
+        if (o instanceof XObject) {
+            return Objects.equals(object, ((XObject)o).getObject());
         }
         return false;
     }
 
+    @Override
+    public int hashCode() {
+        return object.hashCode();
+    }
+
 
     public Object getObject() {
         return object;