拓展赋值运算符、三元运算符

```java
package operator;
//拓展赋值运算符
public class Demo07 {
public static void main(String[] args) {
int a = 10;
int b = 20;

a+=b;//a=a+b

System.out.println(a); //a=30

a-=b; //a=a-b
System.out.println(a); //a=10

//字符串连接符 + ，String
System.out.println(""+a+b); //1020 字符串相加
System.out.println(a+b+""); //30 先计算前面的再加字符串
}
}
```

```java
package operator;
//三元运算符
public class Demo08 {
public static void main(String[] args) {
//x ? y:z
//如果x==ture,则结果为y,否则结果为z

int score = 50;
String type = score<60 ?"不及格":"及格";
System.out.println(type);
}

}
```