java小程序之从方法中返回数组

喜欢ヅ旅行 2022-07-28 00:22 142阅读 0赞

java使用值传递pass by value的方法将实参传递给方法。传递基本数据类型变量的值与传递数组值会有很大的不同。  
1. 传递基本数据类型的参数，传递的是实参的值。  
2. 对于数组类型参数，参数值是数组的引用，给方法传递的是这个引用，参数共享pass-by-sharing。  
从方法中返回数组的代码1：

//将数组逆序输出，传入数组，并从方法中返回数组
    //没有改变原来的数组顺序
    public class Demo032601{
        public static int[] reverse( int[] list ){
            int[] result = new int[ list.length ];
            for (int i = 0, j = list.length-1 ; i < list.length; i++, j-- ){
                result[ j ] = list[ i ];
            }
            return result;
        }
        public static void main( String [] args ){
            int[] list1 = { 2, 4, 5, 7, 9,16 };
            System.out.print( "list1原数组\n" );
            for ( int i = 0; i < list1.length; i++ ){
                System.out.print( list1[i] + "\t" );
            }
            System.out.print( "\n" );
            int[] list2 = reverse( list1 );
            System.out.print( "list2逆序数组\n" );
            for ( int i = 0; i < list2.length; i++ ){
                System.out.print( list2[i] + "\t" );
            }
            System.out.print( "\n" );
            System.out.print( "list1原数组\n" );
            for ( int i = 0; i < list1.length; i++ ){
                System.out.print( list1[i] + "\t" );
            }
            System.out.print( "\n" );
        }
    }

从方法中返回数组的代码2：

//将数组逆序输出，传入数组，并从方法中返回数组
    //改变了原来的数组顺序
    public class Demo032602{
        public static int[] reverse( int[] list ){
            int[] result = new int[ list.length ];
            for (int i = 0, j = list.length-1 ; i < list.length; i++, j-- ){
                result[ j ] = list[ i ];
            }
            for ( int i = 0; i < list.length; i++){
                list[i] = result[i];
            }
            return list;
        }
        public static void main( String [] args ){
            int[] list1 = { 2, 4, 5, 7, 9,16 };
            System.out.print( "list1原数组\n" );
            for ( int i = 0; i < list1.length; i++ ){
                System.out.print( list1[i] + "\t" );
            }
            System.out.print( "\n" );
            int[] list2 = reverse( list1 );
            System.out.print( "list2逆序数组\n" );
            for ( int i = 0; i < list2.length; i++ ){
                System.out.print( list2[i] + "\t" );
            }
            System.out.print( "\n" );
            System.out.print( "list1原数组\n" );
            for ( int i = 0; i < list1.length; i++ ){
                System.out.print( list1[i] + "\t" );
            }
            System.out.print( "\n" );
        }
    }

关于值传递的代码：

//比较传递基本数据类型变量和传递数组值
    public class Demo032603{
        public static void test( int a, int[] b ){
            a = 1000;
            b[0] = 1111;
            System.out.println( "test.a = " + a );
            System.out.println( "test.b[0] = " + b[0] );
        }
        public static void main( String [] args ){
            int x = 1;
            int [] y = { 2 };
            System.out.println( "x = " + x );
            System.out.println( "y[0] = " + y[0] );
            test( x, y );
            System.out.println( "x = " + x );
            System.out.println( "y[0] = " + y[0] );
        }
    }