Add toString() methods

src/main/java/no/birkett/kiwi/Constraint.java

@@ -73,4 +73,9 @@ public class Constraint {
         this.op = op;
     }
 
+    @Override
+    public String toString() {
+        return "expression: (" + expression + ") strength: " + strength + " operator: " + op;
+    }
+
 }

src/main/java/no/birkett/kiwi/Expression.java

@@ -68,5 +68,22 @@ public class Expression {
     public final boolean isConstant() {
         return terms.size() == 0;
     }
+
+    @Override
+    public String toString() {
+        StringBuilder sb = new StringBuilder();
+        sb.append("isConstant: " + isConstant() + " constant: " + constant);
+        if (!isConstant()) {
+            sb.append(" terms: [");
+            for (Term term: terms) {
+                sb.append("(");
+                sb.append(term);
+                sb.append(")");
+            }
+            sb.append("] ");
+        }
+        return sb.toString();
+    }
+
 }
 

src/main/java/no/birkett/kiwi/KiwiException.java

@@ -7,4 +7,7 @@ public class KiwiException extends Exception {
     public KiwiException() {
 
     }
+    public KiwiException(String message) {
+        super(message);
+    }
 }

src/main/java/no/birkett/kiwi/Term.java

@@ -36,4 +36,9 @@ public class Term {
     public double getValue() {
         return coefficient * variable.getValue();
     }
+
+    @Override
+    public String toString() {
+        return "variable: (" + variable + ") coefficient: "  + coefficient;
+    }
 }

src/main/java/no/birkett/kiwi/UnsatisfiableConstraintException.java

@@ -7,6 +7,7 @@ public class UnsatisfiableConstraintException extends KiwiException {
 
     private Constraint constraint;
     public UnsatisfiableConstraintException(Constraint constraint) {
+        super(constraint.toString());
         this.constraint = constraint;
     }
 }

src/main/java/no/birkett/kiwi/Variable.java

@@ -27,4 +27,10 @@ public class Variable {
     public String getName() {
         return name;
     }
+
+    @Override
+    public String toString() {
+        return "name: " + name + " value: " + value;
+    }
+
 }