在java中查找字符串的所有大写字母

Question

所以我试图找到用户输入的字符串中的所有大写字母，但我不断收到运行时错误：

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: 
String index out of range: 4
at java.lang.String.charAt(String.java:686)
at P43.main(P43.java:13)

我觉得很愚蠢，但我无法弄清楚这一点，oracle甚至在java.lang.StringIndexOutOfBoundsException

页面上讨论了charAt

这是我的代码，用于查找大写字母并打印它们：

import java.io.*;
import java.util.*;

public class P43{
   public static void main(String[] args){
      Scanner in = new Scanner(System.in);
      //Uppercase
      String isUp = "";
      System.out.print("Please give a string: ");
      String x = in.next();
      int z = x.length();
      for(int y = 0; y <= z; y++){
         if(Character.isUpperCase(x.charAt(y))){
            char w = x.charAt(y);
            isUp = isUp + w + " ";
         }
      }
      System.out.println("The uppercase characters are " + isUp);
      //Uppercase
   }
}

我真的很感激任何意见和帮助。

Answer 1

for(int y = 0; y <= z; y++){

应该是

for(int y = 0; y < z; y++){

记住数组索引从ZERO开始。

String length返回

  

字符串

中的16位Unicode字符数

因为循环从ZERO开始，循环应终止于长度-1。

Answer 2

数组索引超出范围是因为for循环没有在length - 1上终止，它终止于length 大多数迭代for循环应采用以下形式：

for (int i = 0; i < array.length; i++) {
    // access array[i];
}

字符串也一样。

也许更清洁的方式是：

String inputString; // get user input

String outputString = "";

for (int i = 0; i < inputString.length; i++) {
    c = inputString.charAt(i);
    outputString += Character.isUpperCase(c) ? c + " " : ""; 
}
System.out.println(outputString);

编辑：忘了String没有实现Iterable<Character>，愚蠢的Java。

Answer 3

使用Java 8，您也可以使用lambdas。将String转换为IntStream，使用过滤器仅获取大写字符，并通过将过滤后的字符附加到String来创建新的StringBuilder：

Scanner in = new Scanner(System.in);
System.out.print("Please give a string: ");
//Uppercase
String isUp = in.next()
        .chars()
        .filter((c) -> Character.isUpperCase(c))
        .collect(StringBuilder::new, // supplier
                StringBuilder::appendCodePoint, // accumulator
                StringBuilder::append) // combiner
        .toString();
System.out.println("The uppercase characters are " + isUp);
//Uppercase

灵感来自：

• Adam Bien - Streaming A String
• Simplest way to print anIntStream as a String

Answer 4

试试这个......

方式：

public int findUpperChar(String valitateStr) {
    for (int i = valitateStr.length() - 1; i >= 0; i--) {
        if (Character.isUpperCase(valitateStr.charAt(i))) {
            return i;
        }
    }
    return -1;
}

<强>用法：

String passwordStr = password.getText().toString();

 .......

int len = findUpperChar(passwordStr);

if ( len != -1) {

      capitals exist.   

  } else {

      no capitals exist.            
}

Answer 5

您可以在给定字符串中找到大写字符的简单步骤之一...

<强>程序

import java.io.*;
public class testUpper 
{
    public static void main(String args[]) throws IOException
    {
        String data,answer="";
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        System.out.println("Enter any String : ");
        data=br.readLine();
        char[] findupper=data.toCharArray();
        for(int i=0;i<findupper.length;i++)
        {
            if(findupper[i]>=65&&findupper[i]<=91) //ascii value in between 65 and 91 is A to Z
            {
                answer+=findupper[i]; //adding only uppercase
            }
        }
        System.out.println("Answer : "+answer);
    }
}

<强>输出

输入任何字符串：

欢迎使用String WoRlD

答案：WTHSWRD

Answer 6

您可以在这里增加代码的可读性，并从现代Java的其他功能中受益。请使用Stream方法解决此问题。另外，我建议将最少数量的库导入到您的类中。导入时请避免使用。*。

import React from 'react';
import { StyleSheet, Text, View, Button, TextInput } from 'react-native';

export default class Counter extends React.Component {

state = {
    num: 0,
}

inp1 = 0;
inp2 = 0;

handleSubtract = () => {
    this.setState({
        num:this.inp1-this.inp2
    })
}

handleAdd = () => {
    this.setState({
        num: this.inp1 + this.inp2
    })
}

handleDivide = () => {
    this.setState({
        num: this.inp1 / this.inp2
    })
}

handleMultiply = () => {
    this.setState({
        num: this.inp1 * this.inp2
    })
}

handleTax = () => {

    var newNum = this.num / 100 * 12;

    this.setState({
        num: newNum
    })
}

handleNum1 = (text) => {
    this.inp1 = parseInt(text);
}

handleNum2 = (text) => {
    this.inp2 = parseInt(text);
}

render() {
    return (
        <View style={styles.flexBox}>
            <Text style={styles.flexTitle}>Hi, welcome to my app!</Text>
            <View style={styles.inpBox}>
                <TextInput
                    style={[styles.inps, {marginRight: 10}]}
                    placeholder="Num1"
                    keyboardType="phone-pad"
                    onChangeText={this.handleNum1}
                />
                <TextInput
                    style={styles.inps}
                    placeholder="Num2"
                    keyboardType="phone-pad"
                    onChangeText={this.handleNum2}
                />
            </View>
            <View style={styles.butBox}>
                <View style={styles.button}>
                    <Button
                        onPress={this.handleSubtract}
                        title="Subtract"
                    />
                </View>
                <View style={styles.button}>
                    <Button
                        onPress={this.handleAdd}
                        title="Add"
                    />
                </View>
                <View style={styles.button}>
                    <Button
                        onPress={this.handleMultiply}
                        title="Multiply"
                    />
                </View>
                <View style={styles.button}>
                    <Button
                        onPress={this.handleDivide}
                        title="Divide"
                    />
                </View>
                <View style={[styles.button, {height: 65, width: 65}]}>
                    <Button
                        onPress={this.handleTax}
                        title="Tax"
                        color="#f00"
                />
                </View>
            </View>
            <Text style={styles.numBox}>
                {this.state.num}
            </Text>
        </View>
    );
}
}

const styles = StyleSheet.create({
flexBox: {
    flex: 1,
    flexDirection: "column",
    justifyContent: "center",
    alignItems: "center",
},

flexTitle: {
    padding: 10,
},

inpBox: {
    flexDirection: "row",
},

inps: {
    width: "20%",
    height: 50,
    textAlign: "center",
},

butBox: {
    flexDirection: "row",
    width: "100%",
    alignItems: "center",
},

button: {
    width: "20%",
    height: 50,
},

numBox: {
    padding: 20,
    fontSize: 32,
}
});

示例输入

：

saveChangesInTheEditor

示例输出：

我是

Answer 7

import java.util.Scanner;
class Demo
{
    public static void main(String[] args)
    {
         StringBuilder s=new StringBuilder();
         Scanner input = new Scanner(System.in);
         System.out.println("Enter your String");
         String str= input.nextLine();

         for(int i=0; i<str.length(); i++)
         {
            if(Character.isUpperCase(str.charAt(i)))
            {
               System.out.print(str.charAt(i)+" ");
            }
         }
      }
}

Answer 8

我知道的最简单的方法是使用正则表达式替换。

isUp = x.replaceAll("[^A-Z]", "");

简单来说，它使用一个正则表达式来匹配不在A-Z范围内的任何字符，并将其替换为空字符串。

Answer 9

public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    System.out.println("Enter the number");
    String str= input.nextLine();

    int ascii;
    for(int i=0; i<str.length(); i++) {
        ascii = str.charAt(i);
        System.out.println(ascii);
        if (ascii >= 65 && ascii <= 90) {
            System.out.println("captal letter found ::: "+ascii);
        }
    }
}

Answer 10

public class Cama {

public static void main(String[] args) {
    String camal = "getStudentByName";
    String temp = "";
    for (int i = 0; i < camal.length(); i++) {
        if (Character.isUpperCase(camal.charAt(i))) {
            System.out.print(" " + Character.toLowerCase(camal.charAt(i)));
        } else if (i == 0) {
            System.out.print(Character.toUpperCase(camal.charAt(i)));
        }else{
            System.out.print(camal.charAt(i));
        }
    }
}
}