BAEL-4156 Does a method's signature in Java include its return type? (#10049)

* BAEL-4156 Does a method's signature in Java include its return type?

* BAEL-4156 Add varargs

* Update OverloadingErrors.java

Co-authored-by: Cristian Stancalau <cstancalau@consultant.ffn.com>

core-java-modules/core-java-lang-oop-methods/src/main/java/com/baeldung/signature/OverloadingErrors.java

@@ -0,0 +1,72 @@
+package com.baeldung.signature;
+
+import java.io.Serializable;
+
+public class OverloadingErrors<T extends Serializable> {
+
+    public void print() {
+        System.out.println("Signature is: print()");
+    }
+
+    /*
+    // Uncommenting this method will lead to a compilation error: java: method print() is already defined in class
+    // The method signature is independent from return type
+    public int print() {
+        System.out.println("Signature is: print()");
+        return 0;
+    }
+    */
+
+    /*
+    // Uncommenting this method will lead to a compilation error: java: method print() is already defined in class
+    // The method signature is independent from modifiers
+    private final void print() {
+        System.out.println("Signature is: print()");
+    }
+    */
+
+    /*
+    // Uncommenting this method will lead to a compilation error: java: method print() is already defined in class
+    // The method signature is independent from thrown exception declaration
+    public void print() throws IllegalStateException {
+        System.out.println("Signature is: print()");
+        throw new IllegalStateException();
+    }
+    */
+
+    public void print(int parameter) {
+        System.out.println("Signature is: print(int)");
+    }
+
+    /*
+    // Uncommenting this method will lead to a compilation error: java: method print(int) is already defined in class
+    // The method signature is independent from parameter names
+    public void print(int anotherParameter) {
+        System.out.println("Signature is: print(int)");
+    }
+    */
+
+    public void printElement(T t) {
+        System.out.println("Signature is: printElement(T)");
+    }
+
+    /*
+    // Uncommenting this method will lead to a compilation error: java: name clash: printElement(java.io.Serializable) and printElement(T) have the same erasure
+    // Even though the signatures appear different, the compiler cannot statically bind the correct method after type erasure
+    public void printElement(Serializable o) {
+        System.out.println("Signature is: printElement(Serializable)");
+    }
+    */
+
+    public void print(Object... parameter) {
+        System.out.println("Signature is: print(Object...)");
+    }
+
+    /*
+    // Uncommenting this method will lead to a compilation error: java cannot declare both sum(Object...) and sum(Object[])
+    // Even though the signatures appear different, after compilation they both resolve to sum(Object[])
+    public void print(Object[] parameter) {
+        System.out.println("Signature is: print(Object[])");
+    }
+    */
+}

core-java-modules/core-java-lang-oop-methods/src/main/java/com/baeldung/signature/StaticBinding.java

@@ -0,0 +1,46 @@
+package com.baeldung.signature;
+
+public class StaticBinding {
+
+    public Number sum(Integer term1, Integer term2) {
+        System.out.println("Adding integers");
+        return term1 + term2;
+    }
+
+    public Number sum(Number term1, Number term2) {
+        System.out.println("Adding numbers");
+        return term1.doubleValue() + term2.doubleValue();
+    }
+
+    public Number sum(Object term1, Object term2) {
+        System.out.println("Adding objects");
+        return term1.hashCode() + term2.hashCode();
+    }
+
+    public Number sum(Object term1, Object... term2) {
+        System.out.println("Adding variable arguments: " + term2.length);
+        int result = term1.hashCode();
+        for (Object o : term2) {
+            result += o.hashCode();
+        }
+        return result;
+    }
+
+    public static void main(String[] args) {
+        StaticBinding obj = new StaticBinding();
+
+        obj.sum(2, 3); // "Adding integers" due to auto-boxing from int to Integer
+        obj.sum(Integer.valueOf(2), Integer.valueOf(3)); // "Adding integers" due to exact parameter types
+        obj.sum(2, 0x1); // "Adding integers" due to type promotion from byte to int
+
+        obj.sum((Number) 2, (Number) 3); // "Adding numbers" due to explicit cast to Number
+        obj.sum(2.0d, 3.0d); // "Adding numbers" due to auto-boxing from double to Double
+        obj.sum(Float.valueOf(2), Float.valueOf(3)); // "Adding numbers" due to polimorphism
+
+        obj.sum((Object) 2, (Object) 3); // "Adding objects" due to explicit cast to Object
+        obj.sum(2, "John"); // "Adding objects" due to polimorphism
+
+        obj.sum(new Object(), new Object(), new Object()); // "Adding variable arguments 2"
+        obj.sum(new Object(), new Object[]{new Object()}); // "Adding variable arguments 1"
+    }
+}