[java] 형 변환

String array -> String ArrayList

package com.company;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;

public class test12 {

    public static void main(String[] args) {
        String[] arr = {"A","B"}; // 배열
        List<String> list = new ArrayList<>(Arrays.asList(arr)); // 배열 -> ArrayList
        list.add(1,"C");//인덱스-값 추가

        // 출력 1
        for(int i=0; i<list.size(); i++){ //크기 구하기
            System.out.println(list.get(i));
        }
        System.out.println("-------------------------------");

        //출력 2
        for(String i : list){
            System.out.println(i);
        }
        System.out.println("-------------------------------");
        list.remove(2);// 인덱스 삭제

        //출력 3
        Iterator iter = list.iterator();
        while (iter.hasNext()){
            System.out.println(iter.next());
        }

        System.out.println("-------------------------------");
        //검색
        System.out.println(list.contains("A")); //list에 1이 있는지 검색 : true
        System.out.println(list.indexOf("A")); //1이 있는 index반환 없으면 -1
    }
}

A
C
B
-------------------------------
A
C
B
-------------------------------
A
C
-------------------------------
true
0

 

String -> String 배열

        String str = "hello world";
        char[] a = str.toCharArray();//문자-> 문자 배열

        for(int i=0; i<a.length; i++){
            System.out.println(a[i]);// 출력
        }
/*
h
e
l
l
o
 
w
o
r
l
d
*/

String -> int 배열

package com.company;

import java.util.Arrays;

public class test12 {

    public static void main(String[] args) {
        String str = "12345";
       int[] array = new int[str.length()];
       for(int i=0; i<str.length(); i++){
           array[i] = str.charAt(i)-'0'; //문자 -> int 배열
       }

       // 출력 1
       for(int j=0; j<array.length; j++){
           System.out.println(array[j]);
       }
/*
1
2
3
4
5
*/       
       
       // 출력 2
        System.out.println(Arrays.toString(array));// [1, 2, 3, 4, 5]

    }
}

String -> String 배열 -> int 배열

package com.company;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class test9 {
    public static void main(String[] args) throws IOException {
        BufferedReader rd = new BufferedReader(new InputStreamReader(System.in));
        //string -> string 배열
        String[] a = rd.readLine().split(" ");
        int[] b = new int[a.length];
        int sum =0;
        // string 배열 -> 형 변환 -> int 배열
        for(int i=0; i<a.length; i++){
            b[i] = Integer.parseInt(a[i]);
            sum += b[i];
        }
        System.out.println(sum);

    }//main
}//class

 

 

int -> int 배열

package com.company;

import java.util.Arrays;

public class test12 {

    public static void main(String[] args) {
       // int -> String -> int 배열
        int num = 12345;
        //  1) int -> String
        String str = Integer.toString(num);
       //  2) String -> int 배열
        int[] digit = new int[str.length()];
        for(int i=0; i<str.length();i++){
            digit[i] = str.charAt(i)-'0'; //문자 -> 배열
        }
        System.out.println(Arrays.toString(digit));//출력 [1, 2, 3, 4, 5]
    }
}

https://zetawiki.com/wiki/%EC%9E%90%EB%B0%94_int%EB%A5%BC_%EC%9E%90%EB%A6%BF%EC%88%98_int_%EB%B0%B0%EC%97%B4%EB%A1%9C_%EB%B6%84%ED%95%A0

 

int -> String 방법 2가지 Integer.toString(대상), String.valueOf(대상)

결과

int[] -> String[]

값 하나만 바꿀때 String.valueOf(numbers[i]);

int[] number_array = {6, 10, 2};
String[] string_array = new String[number_array.length];

for(int i=0; i<number_array.length; i++){
 string_array[i] = String.valueOf(number_array[i]);
}

 

int[] -> String

Arrays.toString(array);