知道了char为字符型常量，单引号 ‘ 代表字符

package 第四章;
//filename:App4_2.java
public class App4_2 //定义一个类，名字为App4_2
{
public static void main(String[] args)
{
int testScore=86; //定义一个整型常量testScore=86
char grade; //定义一个字符型grade
if(testScore>=90){ //判断testScore是否大于等于90
grade='A'; //是则grade=A
}else if (testScore>=80){ //否则判断testSroce是否大于等于80
grade='B'; //是则grade=B
}else if (testScore>=70){
grade='C';
}else if (testScore>=60){
grade='D';
}else{
grade='E';
}
System.out.println("评定成绩为"+grade); //输出grade
}
}