배열

java에서의 배열 : index 0부터 시작

int array[]= {1,2,3,4,5};

- index 0,1,2,3,4

- element(요소) : 1,2,3,4,5

 

		int array[]= {1,2,3,4,5};
		
		for( int i=0; i< 5; ++i ) {
			System.out.println(array[i]);
		}

출력

1
2
3
4
5

 

array.length : 길이

		System.out.println(ary.length);

 

		///1~10 합을 구하시오
		int sum=0;
		int ary[]= {1,2,3,4,5,6,7,8,9,10};
		
		for (int i = 0; i < ary.length; i++) {
			
			sum += ary[i];
		}
		System.out.println(sum);

55

 

 

java는 반드시 초기방을 만들어주어야 한다.

	int array[]=new int [10];
	
	int i =0;
	int sum=0;
	do {
		array[i] = i+1;
		sum+= array[i];
		
	} while (++i < array.length);

	System.out.println(sum);

 

 

 

=== 과제 1~20 짝수합, 홀수합

package j20220727;

public class For_While_Do_While {

public static void main(String[] args) {
	int array[]=new int [21];
	
	int i =0;
	int sum=0;
	
	for( ; i < array.length; ++i )
	{
		array[i] = i+1;
		sum+= i;
	}
	System.out.println("전체합:"+sum);
	
	i=0;
	sum=0;
	while( i<array.length ) {
		if( i%2==0)
		sum+= i;
		++i;
	}
	System.out.println("짝수합:"+sum);
	
	i=0;
	sum=0;
	do {
		if( i%2!=0)
		sum+= i;
		++i;
	} while (i<array.length);

	System.out.println("홀수합:"+sum);
}
	
}

 

 

 

 

package j20220727;

public class Array_3 {
	public static void main(String[] args) {
		
		String strarray[]= {"제프조더스","빌게이츠","홍길동","일론머스크"};
		System.out.println(strarray.length);		//length:3
		
		
		for (int i = 0; i < strarray.length; i++) {
			
			//System.out.println(strarray[i]);
		}
		

		for (int i = 0; i < strarray.length; i++) {
			
//			if( i == 2 )
			System.out.println(strarray[i]);
			
			if( strarray[i] == "홍길동" )
				System.out.println(strarray[i]+ " 검색되었습니다.");
			
			
			if(strarray[i].equals("빌게이츠")){
				System.out.println(strarray[i]+ " 검색되었습니다.");
			}
		}
		//System.out.println(strarray[2]);
	}
}

 

 

		char [] charvalue = new char[3];
		//char charvalue [] = new char[3];  //동일
		
		
		charvalue[0]='일';
		charvalue[1]='빌';
		charvalue[2]='김';
		
		//System.out.println(charvalue);
		
		for( int i = 0 ; i < charvalue.length; ++i ){
			System.out.println(charvalue[i]);
		}
		
		System.out.println("===========");
		

		for( int i = 0 ; i < charvalue.length; ++i ){
			System.out.println(charvalue[i]);
			if(charvalue[i] == '김')
			System.out.println(charvalue[i] +" 검색되었습니다.");
		}

 

 

 

 

2차원배열:[][]

행(row), 열(column)

 

 

		int array3[][] = new int[3][3];
		
		for(int i = 0; i < array3.length; ++i ) {
			for(int j = 0; j < array3[i].length; ++j ) {
				
			}
		}

///  각행의 길이 : array3[i].length

		int array3[][] = new int[3][3];
		
		for(int i = 0; i < array3.length; ++i ) {
			for(int j = 0; j < array3[i].length; ++j ) {
				System.out.print("\t 행:" + i + "\t"+j);
			}
			System.out.println();
		}

출력

 행:0 0  행:0 1  행:0 2
 행:1 0  행:1 1  행:1 2
 행:2 0  행:2 1  행:2 2

 

 

 

///3행3열

		int array3_2[][] = {{1,2,3},{4,5,6},{7,8,9}};

		int array3_2[][] = {{1,2,3},{4,5,6},{7,8,9}};
		
		for(int i = 0; i < array3_2.length; ++i ) {
			for(int j = 0; j < array3_2[i].length; ++j ) {
				System.out.print(array3_2[i][j]);
			}
			System.out.println();
		}

출력

123
456
789

 

 

 

 

//과제 : 1~9 합을 구하시오. 2차원 배열 이용해서.