JAVA 高分悬赏

if结构：运用递归
public class jieceng {
public static void main(String[] args){
int jiecheng = jiecheng(10);

System.out.print(jiecheng);
}

public static int jiecheng(int i){
if(i == 1){
return 1;
}
return jiecheng(i-1)*i;
}

}
while结构：
public class jieceng {
public static void main(String[] args){
int jiecheng = jiecheng1(10);

System.out.print(jiecheng);
}

public static int jiecheng1(int i){
int j = 1;
while(i > 1){
j = j*i ;
i--;
}
return j ;
}
}

自己一看语法就明白了。。
4. 2. 7. 嵌套if语句

public class MainClass {

public static void main(String[] arg) {
int a = 2;
if (a == 0) {
System.out.println("in the block");
if (a == 2) {
System.out.println("a is 0");
} else {