if单选结构
public static void main
if(布尔表达式){
}
如果不满足if条件就直接跳过if进入下面的程序
示范程序（改编自狂的示范代码）
public class IfDemon03 {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.println("please writer the number");
String s = scanner.nextLine();
if(s.equals("how is everything going")){
System.out.println("everything is ok ,sir");
}
System.out.println("sir ,you have a phone call ");
scanner.close();
}
}
if双选择结构
if(布尔表达式){
}else{
}
if双选择结构示范代码
public class IfDemon01 {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.println("sir what kind people you want to be?");
String s = scanner.nextLine();
if(s.equals("I want to be the best people")){
System.out.println("you must will be sir");
}else {
System.out.println("trust me sir you are the best keep up");
}
scanner.close();
}
}
if多选择结构
if(布尔表达式1){
///如果布尔表达式1的值为true执行代码
}else if(布尔表达式2){
//如果布尔表达式2的值为true执行代码
}else if(布尔表达式3){
//如果布尔表达式3的值为true执行代码
}else{
//如果以上布尔表达式都不为true执行代码
}/*if 语句至多有一个else语句，并且else语句必须在else if 语句之后
if语句中可以有若干个else if ，一旦其中任何一个else if中的布尔表达式被满足则之后的else if 和else语句都会直接被跳过。
所以这里就要划分清楚每一个if 和 else if 中布尔表达式的判定范围，不要发生重叠。
另外记住表示和的语法是 判断条件1 && 判断条件2
*/
if多选择结构示范代码
public class IfDemon02 {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.println("welcome sir");
String s = scanner.nextLine();
if(s.equals("how is everything going jws")){
System.out.println("everything take on sir");
}else if(s.equals("do you think I'm mad?")){
System.out.println("No sir i thought you good");
}else if(s.equals("jws do you think bowen is fool?")){
System.out.println("yes sir i thought he is");
}else if(s.equals("do you think i can learn over at deadline?")){
System.out.println("yes sir absolutely");
}else if(s.equals("if I don't learn it over,what should I do?")){
System.out.println("keep study sir never give up");
}else{
System.out.println("you are the best sir trust me");
}
scanner.close();
}
}
tips：这里狂使用String 作为数据类型 而后利用是。s.equals("判断相等的语句")来进行判断。
