为什么Java无法在if else语句内的嵌套for循环内打印并显示为终止？

Question

So, I'm writing a program that returns pyramids when you give a word as an input for instance: "Enter a word: " Hello

Justification (L=left, R=Right)? L would print

H

ee

lll

llll

oooo

   import java.util.Scanner;

    public class Justification{   
    public static void main(String[] args) {
    Scanner in= new Scanner(System.in);
    System.out.println("Enter a word: ");
    String word=in.nextLine();
    System.out.println("Justification (L=left, R=Right)?");
    String Justification=in.nextLine();
    if(Justification.equalsIgnoreCase("l")){
            for (int i = 0; i < word.length(); i++) {
                for (int j = 1; j <= i; j++) {
                    System.out.print(word.substring(i,i));
                }
                System.out.println();
            }
    }else if(Justification.equalsIgnoreCase("r")){
         for (int i = word.length()-1; i >= 0; i--) {
             for (int s = 0; s < i; s++) {
                 System.out.print(" ");
             }
             for (int j = word.length()-1; j >= i; j--) {

                 System.out.println(word.substring(i,i));
             }
             System.out.println("");
         }
    }else System.out.println("Bad input");
    }}

Answer 1

You are using substring(begin,end) incorrectly. The character at the begin index is included while the character at the end index is not.

If the word is hello, and you call substring(2,4), it would be ll

String str = "hello".substring(2,4); //str is "ll"

One way to check if substring is used correctly is that endIndex-beginIndex=length of substring . In this case, 4-2=2, so the substring should contain 2 characters, which it does.

An easier way to print out the ith character is to use charAt(i) instead of substring(i,i+1);

System.out.println("hello".substring(0,1)); //prints h
System.out.println("hello".charAt(0));      //also prints h