배열

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배열의 예제 복권뽑기
int[] ball = new int[45];

for (int i =0; i<=ball.length; i++){ball[i]= i+1;}
->ball[0]~ball[44] 0~44 배열에 1~45까지 차례대로 숫자를 넣은것.

int tmp = 0;
int j = 0;

for ( i = 0 ; i < = 6 ; i++)
{

j = Math.random()*45);
tmp = ball[i];
ball[i] = ball[j];
ball[j] = tmp;

}

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2차원 배열 예시

int [][] score =
{

{100, 100},
{20, 20, 20, 20},
{30, 30},
{40, 40}

};

int sum = 0;
for ( int i = 0 ; i < score.length; i++)
{

for( int j = 0 ; j < score [ i ].length; j++)

{ 
	System.out.printf("score[%d][%d]=%d%n", i, j,score[i][j]);
	sum+= score[i][j];
}

}
System.out.println("sum="+sum);

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int [ ] arr = {0, 1, 2, 3, 4};
int [ ][ ] arr2D = { {11, 12}, {21, 22} }

1차원 배열 Arrays.toString(arr));

-> 1차원 배열의 값을 printf 시켜준다.
System.out.printf(Array.toString(arr)); // -> [0, 1, 2, 3, 4]

2차원 배열 Arrays.deepToString(arr));

System.out.printf(Arrays.deepToString(arr2D)); // ->[[11,12],[21,22]]

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배열의 복사 CopyOf( ) , CopyOfRange( )

int[ ] arr = {0,1,2,3,4};

int[ ] arr2 = Arrays.copyOf(arr, arr.length);

-> arr2 = [0,1,2,3,4]

int[ ] arr3 = Arrays.copyOf(arr, 3);

-> arr3 = [0,1,2]

int[ ] arr4 = Arrays.copyOf(arr, 7);

-> arr4 = [0,1,2,3,4,0,0]

int[ ] arr5 = Arrays.copyOfRange(arr, 2, 4);

-> arr5 = [2,3]

int[ ] arr6 = Arrays.copyOfRange(arr, 0, 7);

-> arr6 = [0,1,2,3,4,0,0]

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배열의 정렬 - sort( )

int[ ] arr = {3,2,0,1,4};
Arrays.sort(arr); // arr를 정렬한다.
System.out.println(Arrays.toString(arr));
-> [0,1,2,3,4]