• x++ 返回值为x
• ++x 返回值为x+1
• switch结构无break时，遇到第一个符合情况的case会一直执行至结束
• 赋值语句永远为True

Random(6) [0, 6)

for ( int num : numbers ) { // statements using num}
// is equivalent to
for ( int i = 0; i < numbers.length; i++ ) { 
int num = numbers[i];
// statements using num
}

A 2D array is a 1D array of (reference to ) 1D arrays

Many more useful static methods in Java.lang.Math class

A method’s parameters are considered to be local variables of that method and can be used only in that method’s body.

Method Call Stack

If a series of method calls occurs, the successive return addresses are pushed onto the stack in last-in, first-out order

The program-execution stack also contains the memory for the local variables used in each invocation of a method

◦ Stored in the activation record (or stack frame，活动记录) of the method call