為什么在打印時輸出的一部分沒有顯示？

Question

我正在做的是輸入吉他名稱時會顯示一些規格，例如琴體形狀，琴格數量等。

所以我創建了一個主編碼類

package Guitar;

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        // TODO Auto-generated method stub

        System.out.println("Input name of the guitar");

        Scanner name_g = new Scanner(System.in);
        String name_gf = name_g.next();

        Gibson g = new Gibson();

        System.out.println("Body Shape of the Guitar is : ");
        g.body_shape(name_gf);

        System.out.println("Number of frets of the Guitar is : ");
        g.num_frets(name_gf);

        System.out.println("Neck type of the guitar is : ");
        g.neck_type(name_gf);

        System.out.println("Pickup configuration of the guitar is : ");
        g.pup_conf(name_gf);


    }

}

還有另一種針對吉布森吉他的課程

package Guitar;

public class Gibson extends SpecsVar implements SpecsInterface  {




    @Override
    public String body_shape(String input) {
        // TODO Auto-generated method stub

        System.out.println("Body shape of the guitar is : ");

        if (input.equals(lp)){ 
            return lp;}
        else if (input.equals(ex)){
            return ex;}
        else if (input.equals(sg)){
            return sg;}
        else return "invalid Input.";


    }

    @Override
    public String num_frets(String input) {
        // TODO Auto-generated method stub

        if (input.equals(lp)){ 
            return shrt_fret;}
        else if (input.equals(ex)){
            return shrt_fret;}
        else if (input.equals(sg)){
            return shrt_fret;}
        else return "";

    }

    @Override
    public String neck_type(String input) {
        // TODO Auto-generated method stub

        if (input.equals(lp)){ 
            return mh;}
        else if (input.equals(ex)){
            return rw;}
        else if (input.equals(sg)){
            return rw;}
        else return "";

    }

    @Override
    public String pup_conf(String input) {
        // TODO Auto-generated method stub

        if (input.equals(lp)){ 
            return hh;}
        else if (input.equals(ex)){
            return hh;}
        else if (input.equals(sg)){
            return hh;}
        else return "";

    }

}

然后我上了規格課

package Guitar;

public class SpecsVar {

    //Body Shape
    String lp = "Les Paul";
    String ex = "Explorer";
    String sg = "SG";

    //Number of Frets
    String shrt_fret = "22";
    String lng_fret = "24";

    //Neck Type
    String rw = "Rosewood";
    String mp = "Maple";
    String mh = "Mahogany";

    //Pickup Configuration
    String hsh = "HSH";
    String sss = "SSS";
    String hss = "HSS";
    String hh = "HH";

}

然后是一個界面

package Guitar;

public interface SpecsInterface {

    String body_shape(String input);

    String num_frets(String input);

    String neck_type(String input);

    String pup_conf(String input);

}

這說明發生了什么事

Input name of the guitar
Gibson
Body Shape of the Guitar is : 
Body shape of the guitar is : 
Number of frets of the Guitar is : 
Neck type of the guitar is : 
Pickup configuration of the guitar is : 

當我運行它時，它沒有顯示品格的數量，身體的形狀等。

Answer 1

在System.out.println()您正在執行以下操作：

System.out.println("Body Shape of the Guitar is : ");
g.body_shape(name_gf);

只需移動g.body_shape(name_gf); 進入您的System.out.println()調用，並對其余所有調用執行相同操作。 這稱為字符串串聯

System.out.println("Body Shape of the Guitar is : " + g.body_shape(name_gf));

發生這種情況是因為System.out.println()是實際在屏幕上打印的內容，但第二部分是g.body_shape(name_gf); 只是在進行搜索，而沒有進行其他操作，因此這就是為什么您只需要將其放入打印呼叫中的原因。

Answer 2

更改您的主要看起來像這樣：

public class Main {

  public static void main(String[] args) {
    // TODO Auto-generated method stub

    System.out.println("Input name of the guitar");

    Scanner name_g = new Scanner(System.in);
    String name_gf = name_g.next();

    Gibson g = new Gibson();

    System.out.println("Body Shape of the Guitar is : " + g.body_shape(name_gf));


    System.out.println("Number of frets of the Guitar is : " + g.num_frets(name_gf));


    System.out.println("Neck type of the guitar is : " + g.neck_type(name_gf));


    System.out.println("Pickup configuration of the guitar is : " + g.pup_conf(name_gf));



  }

}

Answer 3

System.out.println("Body Shape of the Guitar is : ");
g.body_shape(name_gf);

第一行正在打印部分消息，但第二行不是。 第二行只是從吉他中獲得一個值，它不顯示它。 將該值連接到消息末尾，如下所示：

System.out.println("Body Shape of the Guitar is : " + g.body_shape(name_gf));

Answer 4

那么這些變量不會被打印出來，因為它們不在print語句中。 您只需要移動g.body_shape(name_gf); 包含在您的打印語句中，例如System.out.println("Body Shape of the Guitar is : " + g.body_shape(name_gf));