자바 시리즈 12 - Scanner 와 String 류 의 사용
91179 단어 Java자바문자열프로 그래 밍 언어
1. Scanner 의 사용
/**
* Scanner
* 1、JDK5 ，
*
* 2、 ：
* public Scanner(InputStream is)
* Scanner sc = new Scanner(System.in);
*
* 3、 ：
* A：hasNextXxx() xxx
* B：nextXxx() xxx
*
* 4、
* nextInt(): int
* next()/nextLine(): String
*
* 5、 ：
* int ---> int
* String ---> String
* String ---> int
* int ---> String
*
* ：
* A： String ， ，
* B： Scanner
* */
import java.util.Scanner;
public class ScannerTest001 {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
if(sc.hasNextInt()) {
int number = sc.nextInt();
System.out.println("number"+number);
}else {
String str1 = sc.nextLine();
System.out.println("str1"+str1);
}
int x = sc.nextInt();
sc = new Scanner(System.in);
String y = sc.nextLine(); //
System.out.println(x);
System.out.println(y);
}
}
2. String 류
/**
* 1、 ：
*
* 2、 ：
* public String(): String
* public String(byte[] bytes):
* public String(byte[] bytes,int index,int length):
* public String(char[] value):
* public String(char[] bytes,int index,int length):
* public String(byte[] bytes):
* public String(String original):
*
* 3、 ：
* 1、 ， toString() 。
* toString() ... @
* ， ， toString()
* 2、
* public int length()
*
* ： length() ？String length() ？
*
*
* 4、 ，
*
* 5、String s = new String("hello"); String s = "hello";
* ==：
* equals()： 。String equals() ，
*
* */
public class StringTest001 {
int number=1;
public static void main(String[] args) {
// public String() String
String s1 = new String();
System.out.println("s1:"+s1);
System.out.println("s1.length():"+s1.length());
System.out.println("--------------------------");
// public String(byte[] bytes): 。
byte[] bytes = { 97, 98, 99, 100, 101 };
String s2 = new String(bytes); //
System.out.println("s2:" + s2);
System.out.println("s2.length():" + s2.length());
System.out.println("--------------------------");
// public String(byte[] bytes,int index,int length):
// String s3 = new String(bytes, 1, 2);
String s3 = new String(bytes, 0, bytes.length);
System.out.println("s3:" + s3);
System.out.println("s3.length():" + s3.length());
System.out.println("--------------------------");
// public String(char[] value):
char[] chs = { 'a', 'b', 'c', 'd', 'e', ' ', ' ', ' ' };
String s4 = new String(chs);
System.out.println("s4:" + s4);
System.out.println("s4.length():" + s4.length());
System.out.println("--------------------------");
// public String(char[] value,int index,int count):
// ： :de
String s5 = new String(chs, 3, 4);
System.out.println("s5:" + s5);
System.out.println("s5.length():" + s5.length());
System.out.println("--------------------------");
// public String(String original):
String s6 = new String("helloworld");
System.out.println("s6:" + s6);
System.out.println("s6.length():" + s6.length());
System.out.println("--------------------------");
// Java （ "abc" ） 。
String s7 = "helloworld";
System.out.println("s7:" + s7);
System.out.println("s7.length():" + s7.length());
// ，
String s8 = "hello";
s8 += "\tworld";
System.out.println("s8:"+s8);
}
// toString, ，
public String toString() {
return "111";
}
}
/**
* == equals
* */
public class StringTest003 {
public static void main(String[] args) {
// == equal
String s1 = new String("abc");
String s2 = new String("abc");
System.out.println(s1==s2); // false
System.out.println(s1.equals(s2)); // true
String s3 = "abc";
String s4 = "abc";
System.out.println(s3==s4); // true
System.out.println(s3.equals(s4)); // true
String s5 = "abc";
String s6 = new String("abc");
System.out.println(s5==s6); // false
System.out.println(s5.equals(s6)); // true
}
}
/**
*
* ： ，
* ： ， ，
* */
public class StringTest004 {
public static void main(String[] args) {
String s1 = "Hello";
String s2 = "World";
String s3 = "HelloWorld";
String s4 = s1 + s2;
String s5 = "Hello" + "World";
System.out.println(s4);
System.out.println(s5);
System.out.println(s3==s4); // false
System.out.println(s3=="Hello"+"World");// true
System.out.println(s3==s5); // true
System.out.println(s3.equals(s4)); // true
System.out.println(s3.equals(s5)); // true
}
}
/**
* String
* boolean equals(Object obj): ，
* boolean equalsIgnoreCase(String str): ，
* boolean contains(String str): ，
* boolean startsWith(Stirng str):
* boolean endsWith(String str):
* boolean isEmpty():
*
* */
public class StringDemo {
public static void main(String[] args) {
String s = "helloworld";
System.out.println(s.equals("helloworld")); // true
System.out.println(s.equals("Helloworld")); // false
System.out.println(s.equalsIgnoreCase("helloworld")); // true
System.out.println(s.equalsIgnoreCase("Helloworld")); // true
System.out.println(s.contains("world")); // true
System.out.println(s.contains("Hello")); // false
System.out.println(s.startsWith("hello")); // true
System.out.println(s.endsWith("wrold")); // false
String s1 = "";
System.out.println(s1.isEmpty()); // true
System.out.println(s1 == ""); // true
}
}
/**
* ：
* ，
* */
import java.util.Scanner;
public class StringTest001 {
public static void main(String[] args) {
String username = "admin";
String password = "admin";
System.out.println("--------------------------");
System.out.println(" ");
System.out.println(" ");
System.out.println(" ");
System.out.println(" ！");
System.out.println("--------------------------");
int i = 3;
while(i>0) {
Scanner sc = new Scanner(System.in);
String sc_username = sc.next();
System.out.println(sc_username);
if (sc_username.equals(username)) {
String sc_password = sc.next();
if (sc_password.equals(password)) {
System.out.println(" ");
break;
}
}
i-=1;
if (i==0) {
System.out.println(" ， ");
}else {
System.out.println(" "+i+" ");
}
}
}
}
/**
* String ：
* int length():
* char charAt(int index):
* int indexOf(int ch):
* int indexOf(Stirng str):
* int indexOf(String str,int fromIndex):
* String substring(int start):
* String substring(int start,int end): ， ：
*
* */
public class StringDemo {
public static void main(String[] args) {
String str1 = "hello";
System.out.println(str1.length()); // 5
System.out.println(str1.charAt(1)); // e
// System.out.println(str1.charAt(10)); // index of range
System.out.println(str1.indexOf('h')); // 0
System.out.println(str1.indexOf("h")); // 0
System.out.println(str1.indexOf('l',3)); // 3
System.out.println(str1.substring(0)); // hello
System.out.println(str1.substring(0,3)); // hel
}
}
/**
* ：
*
*
* */
public class StringTest001 {
public static void main(String[] args) {
String s1 = "HelloWorld";
for(int index=0;index<s1.length();index++) {
System.out.println(" "+index+" "+s1.charAt(index));
}
}
}
/**
* ： ：
*
*
*
*
* */
import java.util.Scanner;
public class StringTest002 {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
String s = sc.next();
int bigCount= 0;
int smallCount= 0;
int intCount= 0;
for(int i=0;i<s.length();i++) {
char ch = s.charAt(i);
if(ch >= 'A' && ch <= 'Z') {
bigCount+=1;
}else if(ch >= 'a' && ch <= 'z') {
smallCount+=1;
}else if(ch >= '0' && ch <= '9') {
intCount+=1;
}
}
System.out.println(" :"+bigCount);
System.out.println(" :"+smallCount);
System.out.println(" :"+intCount);
}
}
package com.bj.study.test006;
/**
* String
* byte[] getBytes():
* char[] toCharArray():
* static String valueOf(char[] chs):
* static String valueOf(int i): int
* 。
* String toLowerCase():
* String toUpperCase():
* String concat(String str):
*
* */
public class StringDemo {
public static void main(String[] args) {
String s = "abcde";
// byte[] getBytes():
byte[] bys = s.getBytes();
for (int x = 0; x < bys.length; x++) {
System.out.println(bys[x]);
}
// char[] toCharArray():
char[] chs = s.toCharArray();
System.out.println(chs);
for (int x = 0; x < chs.length; x++) {
System.out.println(chs[x]);
}
// static String valueOf(char[] chs):
String s2 = String.valueOf(chs);
System.out.println("s2:" + s2);
System.out.println("----------------");
// static String valueOf(int i): int
int number = 100;
String s3 = number + "";
String s4 = String.valueOf(number);
System.out.println("s3:" + s3);
System.out.println("s4:" + s4);
System.out.println("----------------");
// String toLowerCase():
// String toUpperCase():
System.out.println("toLowerCase():" + "HelloWorld11 ".toLowerCase());
System.out.println("toUpperCase():" + "HelloWorld11 ".toUpperCase());
System.out.println("----------------");
// String concat(String str):
String s5 = "hello";
String s6 = "world";
String s7 = s5.concat(s6);
String s8 = s5 + s6;
System.out.println("s7:" + s7);
System.out.println("s8:" + s8);
}
}
/**
* ： ：
* ，
*
* */
import java.util.Scanner;
public class StringTest001 {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
String s = sc.next();
String first = s.substring(0,1).toUpperCase();
String end = s.substring(1).toLowerCase();
String newWords = first+end;
System.out.println(newWords);
}
}
/**
*
* String replace(char old,char new)
* String replace(String old,String new)
*
* ：
* String trim()：
*
* ：a-z
* int compareTo(String str)
* int compareToIgnoreCase(String str)
*
* */
public class StringDemo {
public static void main(String[] args) {
String s = "helloworld";
String s2 = s.replace('l', 'b');
System.out.println("s:" + s);
System.out.println("s2:" + s2);
String s3 = s.replace("owo", "ak47");
String s4 = s.replace("j", "h");
System.out.println("s3:" + s3);
System.out.println("s4:" + s4);
String s5 = " hello ";
System.out.println("s5:" + s5);
System.out.println("s5.trim:" + s5.trim());
String s6 = "hello";
System.out.println(s.compareTo("hello")); // 0
System.out.println(s.compareTo("Hello")); // 32
System.out.println(s.compareTo("mello")); // -5
System.out.println(s.compareTo("hgllo"));// -2
}
}
/**
* ：
* ：int[] arr = {1,2,3}
* ：[1,2,3]
*
* */
public class StringDemo2 {
public static void main(String[] args) {
int[] arr = {1,2,3};
String s = "[";
for(int i=0;i<arr.length;i++) {
if(i==arr.length-1) {
s += arr[i];
}else {
s += arr[i]+",";
}
}
s += "]";
System.out.println(s);
}
}
/**
* ：
* ： abc
* ：cba
* */
import java.util.Scanner;
public class StringDemo3 {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
String s = sc.nextLine();
String result = "";
for (int i=s.length()-1;i>=0;i--) {
result += s.charAt(i);
}
System.out.println(result);
}
}
/**
* 4：
* */
public class StringDemo4 {
public static void main(String[] args) {
String maxString = "woaijavawozhenaijavawozhendeaijavawozhendehenaijavaxinbuxinwoaijavagun";
String minString = "java";
int count = getCount(maxString, minString);
System.out.println(count);
System.out.println("hello".indexOf("z",0));
}
// ：
// :String maxString,String minString;
// :int
public static int getCount(String maxString, String minString) {
//
int count = 0;
//
int index = maxString.indexOf(minString);
// ，
int startIndex = 0;
// -1， ，
while (index != -1) {
// 1
count++;
//
startIndex = index + minString.length();
// ，
index = maxString.indexOf(minString, startIndex);
}
return count;
}
}
package com.bj.study.test007;
/**
* 5： ，
*
* ：
* A：
* B: ， false
* C:
* D：
* */
public class StringDemo5 {
public static void main(String[] args) {
String s1 = "abcdef";
String s2 = "abcd";
boolean result = checkString(s1,s2);
System.out.println(result);
}
private static boolean checkString(String s1, String s2) {
if (s1.length() == s2.length()) {
for(int i=0;i<s1.length();i++) {
if(s1.charAt(i) == s2.charAt(i)) {
return true;
}
}
return false;
}
return false;
}
}
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