java打印数组内容

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发布于 2022-08-11 11:10:37

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代码可运行

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代码可运行

大家好，又见面了，我是你们的朋友全栈君。

在java中直接输出数组只能得到引用地址

byte[] bytes = {
  
  1, 2, 3, 4, 5};
int[] ints = {
  
  1, 2, 3, 4, 5};
System.out.println(bytes);
System.out.println(ints);

输出
[B@1b6d3586
[S@4554617c

打印数组内容, 得到友好的打印

public static void main(String args[]) throws Exception {
        byte[] bytes = {
  
  1, 2, 3, 4, 5};
        short[] shorts = {
  
  1, 2, 3, 4, 5};
        char[] chars = {
  
  'a', 'b', 'c', 'd', 'e'};
        int[] ints = {
  
  1, 2, 3, 4, 5};
        long[] longs = {
  
  1, 2, 3, 4, 5};
        float[] floats = {
  
  1.1F, 2.2F, 3.3F, 4.4F, 5.5F};
        double[] doubles = {
  
  1.1, 2.2, 3.3, 4.4, 5.5};
        String[] strings = {
  
  "aa", "bb", "cc", "dd", "ee", "null"};

        Integer[] integers = {
  
  1, 2, 3, 4, 5};

        int[] ints2 = {};
        int[] ints3 = null;

        List<String> strings1 = new ArrayList<>();
        strings1.add("abc");
        strings1.add("def");
        strings1.add("xyz");
        strings1.add("null");

        Map<Integer, String> map = new HashMap();
        map.put(1, "aa");
        map.put(2, "bb");
        map.put(3, "cc");
        map.put(4, null);

        System.out.println(bytes);
        System.out.println(shorts);
        System.out.println(chars);
        System.out.println(ints);
        System.out.println(longs);
        System.out.println(floats);
        System.out.println(doubles);
        System.out.println(strings);
        System.out.println(integers);
        System.out.println(ints2);
        System.out.println(ints3);
        System.out.println(strings1);
        System.out.println(map);
    }

输出: 

{
  
  1, 2, 3, 4, 5}
{
  
  1, 2, 3, 4, 5}
{a, b, c, d, e}
{
  
  1, 2, 3, 4, 5}
{
  
  1, 2, 3, 4, 5}
{
  
  1.1, 2.2, 3.3, 4.4, 5.5}
{
  
  1.1, 2.2, 3.3, 4.4, 5.5}
{aa, bb, cc, dd, ee, null}
{
  
  1, 2, 3, 4, 5}
{}
{}
[abc, def, xyz, null]
{
  
  1=aa, 2=bb, 3=cc, 4=null}

public class ArrayUtils { 
   

    public static String toString(final Object array) {
        if (array == null) {
            return "{}";
        }
        return new ToStringBuilder().append(array).toString();
    }

    public static class ToStringBuilder { 
   
        private final StringBuffer buffer = new StringBuffer(512);
        private final ToStringStyle style = new ToStringStyle();

        public ToStringBuilder append(final Object obj) {
            style.append(buffer, obj);
            return this;
        }

        @Override
        public String toString() {
            return this.buffer.toString();
        }
    }

    public static class ToStringStyle { 
   
        private char arrayStart = '{';
        private char arrayEnd = '}';
        private String arraySeparator = ", ";

        public void append(final StringBuffer buffer, final Object value) {
            if (value == null) {
                appendNullText(buffer);
            } else {
                appendInternal(buffer, value);
            }
        }

        private void appendNullText(final StringBuffer buffer) {
            buffer.append("");
        }

        private void appendInternal(final StringBuffer buffer, final Object value) {
            register(value);
            try {
                if (value instanceof Collection<?>) {
                    appendDetail(buffer, (Collection<?>) value);
                } else if (value instanceof Map<?, ?>) {
                    appendDetail(buffer, (Map<?, ?>) value);
                } else if (value instanceof long[]) {
                    appendDetail(buffer, (long[]) value);
                } else if (value instanceof int[]) {
                    appendDetail(buffer, (int[]) value);
                } else if (value instanceof short[]) {
                    appendDetail(buffer, (short[]) value);
                } else if (value instanceof byte[]) {
                    appendDetail(buffer, (byte[]) value);
                } else if (value instanceof char[]) {
                    appendDetail(buffer, (char[]) value);
                } else if (value instanceof double[]) {
                    appendDetail(buffer, (double[]) value);
                } else if (value instanceof float[]) {
                    appendDetail(buffer, (float[]) value);
                } else if (value instanceof boolean[]) {
                    appendDetail(buffer, (boolean[]) value);
                } else if (value.getClass().isArray()) {
                    appendDetail(buffer, (Object[]) value);
                } else {
                    appendDetail(buffer, value);
                }
            } finally {
                unregister(value);
            }
        }

        private static final ThreadLocal<WeakHashMap<Object, Object>> REGISTRY =
                new ThreadLocal<>();

        private static Map<Object, Object> getRegistry() {
            return REGISTRY.get();
        }

        private static void register(final Object value) {
            if (value != null) {
                final Map<Object, Object> m = getRegistry();
                if (m == null) {
                    REGISTRY.set(new WeakHashMap<>());
                }
                getRegistry().put(value, null);
            }
        }

        static void unregister(final Object value) {
            if (value != null) {
                final Map<Object, Object> m = getRegistry();
                if (m != null) {
                    m.remove(value);
                    if (m.isEmpty()) {
                        REGISTRY.remove();
                    }
                }
            }
        }

        private void appendDetail(final StringBuffer buffer, final boolean[] array) {
            buffer.append(arrayStart);
            for (int i = 0; i < array.length; i++) {
                if (i > 0) {
                    buffer.append(arraySeparator);
                }
                appendDetail(buffer, array[i]);
            }
            buffer.append(arrayEnd);
        }

        private void appendDetail(final StringBuffer buffer, final byte[] array) {
            buffer.append(arrayStart);
            for (int i = 0; i < array.length; i++) {
                if (i > 0) {
                    buffer.append(arraySeparator);
                }
                appendDetail(buffer, array[i]);
            }
            buffer.append(arrayEnd);
        }

        private void appendDetail(final StringBuffer buffer, final short[] array) {
            buffer.append(arrayStart);
            for (int i = 0; i < array.length; i++) {
                if (i > 0) {
                    buffer.append(arraySeparator);
                }
                appendDetail(buffer, array[i]);
            }
            buffer.append(arrayEnd);
        }

        private void appendDetail(final StringBuffer buffer, final char[] array) {
            buffer.append(arrayStart);
            for (int i = 0; i < array.length; i++) {
                if (i > 0) {
                    buffer.append(arraySeparator);
                }
                appendDetail(buffer, array[i]);
            }
            buffer.append(arrayEnd);
        }

        private void appendDetail(final StringBuffer buffer, final int[] array) {
            buffer.append(arrayStart);
            for (int i = 0; i < array.length; i++) {
                if (i > 0) {
                    buffer.append(arraySeparator);
                }
                appendDetail(buffer, array[i]);
            }
            buffer.append(arrayEnd);
        }

        private void appendDetail(final StringBuffer buffer, final float[] array) {
            buffer.append(arrayStart);
            for (int i = 0; i < array.length; i++) {
                if (i > 0) {
                    buffer.append(arraySeparator);
                }
                appendDetail(buffer, array[i]);
            }
            buffer.append(arrayEnd);
        }

        private void appendDetail(final StringBuffer buffer, final double[] array) {
            buffer.append(arrayStart);
            for (int i = 0; i < array.length; i++) {
                if (i > 0) {
                    buffer.append(arraySeparator);
                }
                appendDetail(buffer, array[i]);
            }
            buffer.append(arrayEnd);
        }

        private void appendDetail(final StringBuffer buffer, final Collection<?> coll) {
            buffer.append(coll);
        }

        private void appendDetail(final StringBuffer buffer, final Map<?, ?> map) {
            buffer.append(map);
        }

        private void appendDetail(final StringBuffer buffer, final long[] array) {
            buffer.append(arrayStart);
            for (int i = 0; i < array.length; i++) {
                if (i > 0) {
                    buffer.append(arraySeparator);
                }
                appendDetail(buffer, array[i]);
            }
            buffer.append(arrayEnd);
        }

        private void appendDetail(final StringBuffer buffer, final Object value) {
            buffer.append(value);
        }

        private void appendDetail(final StringBuffer buffer, final Object[] array) {
            buffer.append(arrayStart);
            for (int i = 0; i < array.length; i++) {
                final Object item = array[i];
                if (i > 0) {
                    buffer.append(arraySeparator);
                }
                if (item == null) {
                    appendNullText(buffer);
                } else {
                    appendInternal(buffer, item);
                }
            }
            buffer.append(arrayEnd);
        }
    }
}