Java 7 documentation:

Returns the smaller of two int values. That is, the result the argument closer to the value of Integer.MIN_VALUE. If the arguments have the same value, the result is that same value.

Behaviour:

Math.min(1, 2) => 1
Math.min(1F, 2) => 1F
Math.min(3D, 2F) => 2D
Math.min(-0F, 0F) => -0F
Math.min(0D, -0D) => -0D
Math.min(Float.NaN, -2) => Float.NaN
Math.min(-2F, Double.NaN) => Double.NaN

java.lang.Math and java.lang.StrictMath Source:

public static int min(int a, int b) {
    return (a <= b) ? a : b;
}

java.lang.Math Bytecode (javap -c Math.class of Oracle's JDK's JRE's rt.jar):

public static int min(int, int);
Code:
   0: iload_0           // loads a onto the stack
   1: iload_1           // loads b onto the stack
   2: if_icmpgt     9   // pops two ints (a, b) from the stack
                        // and compares them
                        // if b>a, the jvm continues at label 9
                        // else, at the next instruction, 5
                        // icmpgt is for integer-compare-greater-than
   5: iload_0           // loads a onto the stack
   6: goto          10  // jumps to label 10
   9: iload_1           // loads 
  10: ireturn           // returns the currently loaded integer

If the comparison at 5 is true, a will be loaded, the jvm will jump to 10 and return a, if the comparison yields false, it will jump to 9, which will load and return b.

Intrinsics:

This .hpp file of the Java 8 Hotspot JVM hints that it optimizes Math.min even further with optimized machine code:

do_intrinsic(_min, java_lang_Math, min_name, int2_int_signature, F_S)

This means the above bytecode won't be executed by the Java 8 Hotspot JVM. However, this differs from JVM to JVM, which is why I also explained the bytecode!

Hopefully, now you know all there is to know about Math.min! :)