Java笔试--代码纠错

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package practice.javase;
public abstract class Name {
private String name;
public abstract boolean isStupidName(String name){};
}

错误：编译无法通过，原因抽象方法不能有方法体；改正，将抽象方法改为普通方法，或去掉方法体；

package practice.javase;
public abstract class Name {
private String name;
public abstract boolean isStupidName(String name);;
}

package practice.javase;
public abstract class Name {
private String name;
public boolean isStupidName(String name){
return false;};
}

package practice.javase;
public class Something {
void doSomething(){
private String s = "";
int l = s.length();
}
}

错误：编译无法通过，原因局部变量不能有权限修饰符，权限修饰符是为了设置访问权限而设定的，局部变量的访问权限已经确定是在方法体内了，故错误，改正，去掉权限修饰符；

package practice.javase;
public class Something {
void doSomething(){
String s = "";
int l = s.length();
}
}

package practice.javase;
public abstract class Something1 {
private abstract String doSomething();
}

错误:编译无法通过,原因抽象类中的抽象方法是要被其子类继承和重写的,所以权限只能是public或者protected,或者默认权限,不能使private,private不能被其他类访问,和抽象本意冲突,没有意义;

package practice.javase;
public abstract class Something1 {
abstract String doSomething();
}

package practice.javase;
public class Something2 {
public static void main(String[] args) {
Something2 something2 = new Something2();
something2.doString();
System.out.println("something2.doString return"+doString());
} public String doString(){
return "Do SomeString.....";
}
}

错误:静态方法中不能调用非静态的方法或成员变量,如果想调用,只能通过对象调用,因为他是实例方法不是类方法;

package practice.javase;
public class Something2 {
public static void main(String[] args) {
Something2 something2 = new Something2();
something2.doString();
System.out.println("something2.doString return"+something2.doString());
} public String doString(){
return "Do SomeString.....";
}
}

此处Somestring3类的文件名是OtherString.java
package practice.javase;
public class Something3 {
private static void main(String[] something_to_do){
System.out.println("Do Something....");
}
}

错误:这段代码编译不会报错,但是我们注意一个问题Somestring3类的文件名是OtherString.java,那么就一定不正确,java的机制是编译后生成.java文件,解释器解释成二进制文件

package practice.javase;
public class OtherString {
private static void main(String[] something_to_do){
System.out.println("Do Something....");
}
}

package practice.javase;
public interface A {
int x = 0;
}
package practice.javase;
public class B {
int x = 1;
}
package practice.javase;
public class C extends B implements A{
public void pX(){
System.out.println(x);
}
public static void main(String[] args) {
new C().pX();
}
}

Class C编译报错:
接口的含义理解:接口可以理解成统一的"协议",而接口中的属性也属于协议中的内容;但是接口的属性都是公共的,静态的,最终的
接口的成员特点：
A:成员变量只能是常量。默认修饰符 public static final
B:成员方法只能是抽象方法。默认修饰符 public abstract
推荐：永远手动给出修饰符。
在Class C中继承了B,继承了B中非私有的方法和属性,但要通过super关键字来调用父类中的成员变量和方法;

package practice.javase;
public class C extends B implements A{
public void pX(){
System.out.println(super.x);
}
public static void main(String[] args) {
new C().pX();
}
}

package practice.javase;
public interface Playable {
void play();
}package practice.javase;
public interface Bounceable {
void play();
}package practice.javase;
public interface Rollable extends Playable, Bounceable{
Ball ball = new Ball("PingPang");
}package practice.javase;
public class Ball implements Rollable{
private String name;
public Ball(String name) {
super();
this.name = name;
}
public String getName() {
return name;
} public void play(){
ball = new Ball("FootBall");
System.out.println(ball.getName());
}}错误:编译错误,错误在ball = new Ball("FootBall");,变量未经声明,

package practice.javase;
public class Ball implements Rollable{
private String name;
public Ball(String name) {
super();
this.name = name;
}
public String getName() {
return name;
} public void play(){
Ball ball = new Ball("FootBall");
System.out.println(ball.getName());
}}