switch

1. Supported Functionality

Supports conditional branches for byte, short, int, char, String, and enum.

2. Source Analysis

2.1. int

int a = 5;
switch (a)
{
    case 1:
        System.out.println(1);
        break;
    case 5:
        System.out.println(5);
        break;
    default:
        break;
}

After compilation, viewing the class file with IDEA shows no change, which indicates that int values are compared directly.

2.2. char

char a = 'b';
switch (a)
{
    case 'a':
        System.out.println('a');
        break;
    case 'b':
        System.out.println('b');
        break;
    default:
        break;
}

• After decompilation

char a = 98;
switch(a) {
case 97:
    System.out.println('a');
    break;
case 98:
    System.out.println('b');
}

The ASCII code of the char is compared.

2.3. String

String str = "world";
switch (str)
{
    case "hello":
        System.out.println("hello");
        break;
    case "world":
        System.out.println("world");
        break;
    default:
        break;
}

• After decompilation

String str = "world";
byte var3 = -1;
switch(str.hashCode()) {
case 99162322:
    if (str.equals("hello")) {
        var3 = 0;
    }
    break;
case 113318802:
    if (str.equals("world")) {
        var3 = 1;
    }
}

switch(var3) {
case 0:
    System.out.println("hello");
    break;
case 1:
    System.out.println("world");
}

It first compares the String’s hashCode, then uses equals to compare for equality.