1. char is promoted to int;

2. byte is promoted to short;

3. The constant value 5 is treated as an int, so if an overloaded method is available that takes an int, it its used.

4. In all other cases, if you have a data type that is smaller than the argument in the method, that type is promoted.

5. If your argument is wider than what the method expects, you must perform a narrawing conversion with a cast. If you don't do this, the compiler will issue an error message.

// housekeeping/PrimitiveOverloading.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
// Promotion of primitives and overloading

public class PrimitiveOverloading {
  void f1(char x) {
    System.out.print("f1(char) ");
  }

  void f1(byte x) {
    System.out.print("f1(byte) ");
  }

  void f1(short x) {
    System.out.print("f1(short) ");
  }

  void f1(int x) {
    System.out.print("f1(int) ");
  }

  void f1(long x) {
    System.out.print("f1(long) ");
  }

  void f1(float x) {
    System.out.print("f1(float) ");
  }

  void f1(double x) {
    System.out.print("f1(double) ");
  }

  void f2(byte x) {
    System.out.print("f2(byte) ");
  }

  void f2(short x) {
    System.out.print("f2(short) ");
  }

  void f2(int x) {
    System.out.print("f2(int) ");
  }

  void f2(long x) {
    System.out.print("f2(long) ");
  }

  void f2(float x) {
    System.out.print("f2(float) ");
  }

  void f2(double x) {
    System.out.print("f2(double) ");
  }

  void f3(short x) {
    System.out.print("f3(short) ");
  }

  void f3(int x) {
    System.out.print("f3(int) ");
  }

  void f3(long x) {
    System.out.print("f3(long) ");
  }

  void f3(float x) {
    System.out.print("f3(float) ");
  }

  void f3(double x) {
    System.out.print("f3(double) ");
  }

  void f4(int x) {
    System.out.print("f4(int) ");
  }

  void f4(long x) {
    System.out.print("f4(long) ");
  }

  void f4(float x) {
    System.out.print("f4(float) ");
  }

  void f4(double x) {
    System.out.print("f4(double) ");
  }

  void f5(long x) {
    System.out.print("f5(long) ");
  }

  void f5(float x) {
    System.out.print("f5(float) ");
  }

  void f5(double x) {
    System.out.print("f5(double) ");
  }

  void f6(float x) {
    System.out.print("f6(float) ");
  }

  void f6(double x) {
    System.out.print("f6(double) ");
  }

  void f7(double x) {
    System.out.print("f7(double) ");
  }

  void testConstVal() {
    System.out.print("5: ");
    f1(5);
    f2(5);
    f3(5);
    f4(5);
    f5(5);
    f6(5);
    f7(5);
    System.out.println();
  }

  void testChar() {
    char x = 'x';
    System.out.print("char: ");
    f1(x);
    f2(x);
    f3(x);
    f4(x);
    f5(x);
    f6(x);
    f7(x);
    System.out.println();
  }

  void testByte() {
    byte x = 0;
    System.out.print("byte: ");
    f1(x);
    f2(x);
    f3(x);
    f4(x);
    f5(x);
    f6(x);
    f7(x);
    System.out.println();
  }

  void testShort() {
    short x = 0;
    System.out.print("short: ");
    f1(x);
    f2(x);
    f3(x);
    f4(x);
    f5(x);
    f6(x);
    f7(x);
    System.out.println();
  }

  void testInt() {
    int x = 0;
    System.out.print("int: ");
    f1(x);
    f2(x);
    f3(x);
    f4(x);
    f5(x);
    f6(x);
    f7(x);
    System.out.println();
  }

  void testLong() {
    long x = 0;
    System.out.print("long: ");
    f1(x);
    f2(x);
    f3(x);
    f4(x);
    f5(x);
    f6(x);
    f7(x);
    System.out.println();
  }

  void testFloat() {
    float x = 0;
    System.out.print("float: ");
    f1(x);
    f2(x);
    f3(x);
    f4(x);
    f5(x);
    f6(x);
    f7(x);
    System.out.println();
  }

  void testDouble() {
    double x = 0;
    System.out.print("double: ");
    f1(x);
    f2(x);
    f3(x);
    f4(x);
    f5(x);
    f6(x);
    f7(x);
    System.out.println();
  }

  public static void main(String[] args) {
    PrimitiveOverloading p = new PrimitiveOverloading();
    p.testConstVal();
    p.testChar();
    p.testByte();
    p.testShort();
    p.testInt();
    p.testLong();
    p.testFloat();
    p.testDouble();
  }
}
/* Output:
5: f1(int) f2(int) f3(int) f4(int) f5(long) f6(float) f7(double)

char: f1(char) f2(int) f3(int) f4(int) f5(long) f6(float) f7(double)
byte: f1(byte) f2(byte) f3(short) f4(int) f5(long) f6(float) f7(double)

short: f1(short) f2(short) f3(short) f4(int) f5(long) f6(float) f7(double)
int: f1(int) f2(int) f3(int) f4(int) f5(long) f6(float) f7(double)
long: f1(long) f2(long) f3(long) f4(long) f5(long) f6(float) f7(double)
float: f1(float) f2(float) f3(float) f4(float) f5(float) f6(float) f7(double)
double: f1(double) f2(double) f3(double) f4(double) f5(double) f6(double) f7(double)
*/

references:

1. https://github.com/wangbingfeng/OnJava8-Examples/blob/master/housekeeping/PrimitiveOverloading.

2. https://github.com/wangbingfeng/OnJava8-Examples/blob/master/housekeeping/Demotion.java

3. On Java 8 - Bruce Eckel