Java 名称…；）嘿确保你的答案中有一些单词，并告诉我们为什么你的答案有效或应该有效，以使提问者理解。非常详细的解释。 Scanner reader = new Scanner(System.in) String inp = reader.next

---

名称…；）嘿确保你的答案中有一些单词，并告诉我们为什么你的答案有效或应该有效，以使提问者理解。非常详细的解释。

    Scanner reader = new Scanner(System.in)
    String inp = reader.nextLine();
            String inputName1;
            inputName1 = inp.substring(int i = (int)(Math.random()*(inp.length()-0)+0), i+=1);

public class Knuth { 

// this class should not be instantiated
private Knuth() { }

/**
 * Rearranges an array of objects in uniformly random order
 * (under the assumption that <tt>Math.random()</tt> generates independent
 * and uniformly distributed numbers between 0 and 1).
 * @param a the array to be shuffled
 */
public static void shuffle(Object[] a) {
    int N = a.length;
    for (int i = 0; i < N; i++) {
        // choose index uniformly in [i, N-1]
        int r = i + (int) (Math.random() * (N - i));
        Object swap = a[r];
        a[r] = a[i];
        a[i] = swap;
    }
}

/**
 * Reads in a sequence of strings from standard input, shuffles
 * them, and prints out the results.
 */
public static void main(String[] args) {

    // read in the data
    String[] a = StdIn.readAllStrings();

    // shuffle the array
    Knuth.shuffle(a);

    // print results.
    for (int i = 0; i < a.length; i++)
        StdOut.println(a[i]);
}

Scanner keyboard = new Scanner(System.in);
String inp = keyboard.nextLine();
Random generator = new Random();
String newString = ""; //contains the extracted letters
int randomPositionOfLetter; 
for(int i=1;i<=3;i++){
    // calculating a random position of a char in the string
    randomPositionOfLetter = generator.nextInt(inp.length());
    newString = newString + inp.charAt(randomPositionOfLetter);
}

import java.util.Scanner; public class Test { public static void main( String args[] ){ Scanner reader = new Scanner(System.in); String inp = reader.nextLine(); java.util.Random rnd = new java.util.Random(); int i = rnd.nextInt(inp.length()), j = rnd.nextInt(inp.length()), k = rnd.nextInt(inp.length()); System.out.println("Letter 1: "+inp.charAt(i)+", Letter 2: "+inp.charAt(j)+" and Letter 3: "+inp.charAt(k)); } }

   public class GenerateString {

    public static void main(String[] args) {        
        generateChars(3);
    }
    /**
     * get input from user at start
     * */
    public static String getInputString(int length) {
        System.out.println("Put your String to get " +  length + " random chars: ");
        Scanner input = new Scanner(System.in);
        String userInput = input.nextLine();

        if(userInput.length() < length) {
            System.out.println("Your input is less than " + length + ".");
            userInput = getInputString(length);
        }

        return userInput;
    }

    /**
     * generate chars with the given length
     * */
    public static void generateChars(int length) {

        String input = getInputString(length);
        int i = 0;
        int inputLength = input.length();
        StringBuilder stringBuilder = new StringBuilder();
        while(i < length) {
            char randomChar = input.charAt(getRandomPosition(inputLength));
            stringBuilder.append(randomChar);
            i++;
        }
        System.out.println("Your random string is: " + stringBuilder.toString());
        stop(length);
    }

    /**
     * get random position
     * */
    public static int getRandomPosition(int length) {
        Random generator = new Random();
        return generator.nextInt(length);
    }

    /**
     * stop the program
     * */
    public static void stop(int length) {
        System.out.println("Do you want to stop? Press 2 to continue, press any number to exit.");
        Scanner input = new Scanner(System.in);
        try {
            int in = input.nextInt();
            if(in == 2) {
                generateChars(length);
            } else {
                System.exit(1);
            }   
        } catch(Exception ex){
            System.out.println("Input is not number!");
            stop(length);
        }

    }
}

    Scanner reader = new Scanner(System.in);
    String inp = reader.nextLine();
    char[] chars = new char[3];

    for(int x = 0; x < 3; x++){
        chars[x] = inp.charAt(ThreadLocalRandom.current().nextInt(0, inp.length()));  
    }

    System.out.println(Arrays.toString(chars));