基本类型

public class Foo {
    public static void main(String[] args) {
        boolean flag = true;
        if (flag) System.out.println("Hello, Java!");
        if (flag == true) System.out.println("Hello, JVM!");
    }
}

$ javac Foo.java

$ java Foo
Hello, Java!
Hello, JVM!

# jasm与javap的输出比较类似
$ java -cp ./asmtools.jar org.openjdk.asmtools.jdis.Main Foo.class > Foo.jasm.bak

$ tail -n 23 Foo.jasm.bak | head -n 21
public static Method main:"([Ljava/lang/String;)V"
	stack 2 locals 2
{
		iconst_1;
		istore_1;
		iload_1;
		ifeq	L14; # 出栈int，如果等于0时跳转；实际为1，无需跳转
		getstatic	Field java/lang/System.out:"Ljava/io/PrintStream;";
		ldc	String "Hello, Java!";
		invokevirtual	Method java/io/PrintStream.println:"(Ljava/lang/String;)V";
	L14:	stack_frame_type append;
		locals_map int;
		iload_1;
		iconst_1;
		if_icmpne	L27; # 出栈2个int，如果不相等时跳转；实际为1和1，无需跳转
		getstatic	Field java/lang/System.out:"Ljava/io/PrintStream;";
		ldc	String "Hello, JVM!";
		invokevirtual	Method java/io/PrintStream.println:"(Ljava/lang/String;)V";
	L27:	stack_frame_type same;
		return;
}

$ awk 'NR==1,/iconst_1/{sub(/iconst_1/, "iconst_2")} 1' Foo.jasm.bak > Foo.jasm

$ tail -n 23 Foo.jasm.bak | head -n 21
public static Method main:"([Ljava/lang/String;)V"
	stack 2 locals 2
{
		iconst_2; # iconst_1 -> iconst_2
		istore_1;
		iload_1;
		ifeq	L14; # 出栈int，如果等于0时跳转；实际为1，无需跳转
		getstatic	Field java/lang/System.out:"Ljava/io/PrintStream;";
		ldc	String "Hello, Java!";
		invokevirtual	Method java/io/PrintStream.println:"(Ljava/lang/String;)V";
	L14:	stack_frame_type append;
		locals_map int;
		iload_1;
		iconst_1;
		if_icmpne	L27; # 出栈2个int，如果不相等时跳转；实际为1和2，需跳转
		getstatic	Field java/lang/System.out:"Ljava/io/PrintStream;";
		ldc	String "Hello, JVM!";
		invokevirtual	Method java/io/PrintStream.println:"(Ljava/lang/String;)V";
	L27:	stack_frame_type same;
		return;
}

$ java -cp ./asmtools.jar org.openjdk.asmtools.jasm.Main Foo.jasm

$ java Foo
Hello, Java!

private static String floatToHexIntBits(float f) {
    return Integer.toHexString(Float.floatToIntBits(f));
}

float z1 = +0.0F; // +0.0F
float z2 = -0.0F; // -0.0F
log.info("{}", floatToHexIntBits(z1)); // 0
log.info("{}", floatToHexIntBits(z2)); // 0x80000000
log.info("{}", z1 == z2); // 两个0对应的内存数值不同，但+0.0F == -0.0F

public static final float POSITIVE_INFINITY = 1.0f / 0.0f;
public static final float NEGATIVE_INFINITY = -1.0f / 0.0f;
log.info("{}", floatToHexIntBits(Float.POSITIVE_INFINITY)); // 0x7F800000
log.info("{}", floatToHexIntBits(Float.NEGATIVE_INFINITY)); // 0XFF800000

float f = 1.0F;
log.info("{}", floatToHexIntBits(NaN)); // 0x7FC00000
log.info("{}", NaN < f);    // false
log.info("{}", NaN >= f);   // false
log.info("{}", NaN != f);   // true
log.info("{}", NaN == f);   // false
log.info("{}", NaN == NaN); // false

@Slf4j
@Data
public class User {
    private boolean sex;

    public static void main(String[] args) throws NoSuchFieldException, IllegalAccessException {
        Field field = Unsafe.class.getDeclaredField("theUnsafe");
        field.setAccessible(true);
        Unsafe unsafe = (Unsafe) field.get(null);

        User user = new User();
        Field sexField = User.class.getDeclaredField("sex");

        unsafe.putByte(user, unsafe.objectFieldOffset(sexField), (byte) 2);
        log.info("{}", user.isSex()); // 10 -> 0 , false

        unsafe.putByte(user, unsafe.objectFieldOffset(sexField), (byte) 3);
        log.info("{}", user.isSex()); // 11 -> 1 , true
    }
}