Description Manoj N Palat 2021-08-26 19:04:22 EDT

Issue by Remi Forax

import static java.util.stream.IntStream.rangeClosed;

public interface PatternFizzBuzz {
  static String fizzbuzz(int i) {
    return switch((Integer) i) {
      case Integer v && v % 15 == 0 -> "FizzBuzz";
      case Integer v && v % 5 == 0 -> "Buzz";
      case Integer v && v % 3 == 0 -> "Fizz";
      case Integer v -> "" + v;
    };
  }

  static void main(String[] args) {
    rangeClosed(1, 100).mapToObj(i -> fizzbuzz(i)).forEach(System.out::println);
  }
}

the code generated by eclipse is full of unnecessary casts
(see the <-- here)

public static java.lang.String fizzbuzz(int);
    Code:
       0: iload_0
       1: invokestatic  #8                  // Method java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
       4: astore_1
       5: iconst_0
       6: istore_2
       7: aload_1
       8: iload_2
       9: invokedynamic #14,  0             // InvokeDynamic #0:typeSwitch:(Ljava/lang/Object;I)I
      14: tableswitch   { // -1 to 2
                    -1: 121
                     0: 44
                     1: 69
                     2: 95
               default: 121
          }
      44: aload_1
      45: checkcast     #9                  // class java/lang/Integer   <-- here
      48: astore_3
      49: aload_3
      50: invokevirtual #18                 // Method java/lang/Integer.intValue:()I
      53: bipush        15
      55: irem
      56: ifeq          64
      59: iconst_1
      60: istore_2
      61: goto          7
      64: ldc           #22                 // String FizzBuzz
      66: goto          139
      69: aload_1
      70: checkcast     #9                  // class java/lang/Integer  <-- here
      73: astore        4
      75: aload         4
      77: invokevirtual #18                 // Method java/lang/Integer.intValue:()I
      80: iconst_5
      81: irem
      82: ifeq          90
      85: iconst_2
      86: istore_2
      87: goto          7
      90: ldc           #24                 // String Buzz
      92: goto          139
      95: aload_1
      96: checkcast     #9                  // class java/lang/Integer  <-- here
      99: astore        5
     101: aload         5
     103: invokevirtual #18                 // Method java/lang/Integer.intValue:()I
     106: iconst_3
     107: irem
     108: ifeq          116
     111: iconst_3
     112: istore_2
     113: goto          7
     116: ldc           #26                 // String Fizz
     118: goto          139
     121: aload_1
     122: astore        6
     124: new           #28                 // class java/lang/StringBuilder
     127: dup
     128: invokespecial #30                 // Method java/lang/StringBuilder."<init>":()V
     131: aload         6
     133: invokevirtual #34                 // Method java/lang/StringBuilder.append:(Ljava/lang/Object;)Ljava/lang/StringBuilder;
     136: invokevirtual #38                 // Method java/lang/StringBuilder.toString:()Ljava/lang/String;
     139: areturn


if you compare with the one generated by javac

public interface PatternFizzBuzz {
  public static java.lang.String fizzbuzz(int);
    Code:
       0: iload_0
       1: invokestatic  #1                  // Method java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
       4: astore_1
       5: iconst_0
       6: istore_2
       7: aload_1
       8: iload_2
       9: invokedynamic #7,  0              // InvokeDynamic #0:typeSwitch:(Ljava/lang/Object;I)I
      14: tableswitch   { // -1 to 2
                    -1: 112
                     0: 44
                     1: 66
                     2: 89
               default: 112
          }
      44: aload_1
      45: astore_3
      46: aload_3
      47: invokevirtual #11                 // Method java/lang/Integer.intValue:()I
      50: bipush        15
      52: irem
      53: ifeq          61
      56: iconst_1
      57: istore_2
      58: goto          7
      61: ldc           #15                 // String FizzBuzz
      63: goto          125
      66: aload_1
      67: astore        4
      69: aload         4
      71: invokevirtual #11                 // Method java/lang/Integer.intValue:()I
      74: iconst_5
      75: irem
      76: ifeq          84
      79: iconst_2
      80: istore_2
      81: goto          7
      84: ldc           #17                 // String Buzz
      86: goto          125
      89: aload_1
      90: astore        5
      92: aload         5
      94: invokevirtual #11                 // Method java/lang/Integer.intValue:()I
      97: iconst_3
      98: irem
      99: ifeq          107
     102: iconst_3
     103: istore_2
     104: goto          7
     107: ldc           #19                 // String Fizz
     109: goto          125
     112: aload_1
     113: astore        6
     115: aload         6
     117: invokedynamic #21,  0             // InvokeDynamic #1:makeConcatWithConstants:(Ljava/lang/Integer;)Ljava/lang/String;
     122: goto          125
     125: areturn