/**
* Returns the string representation of this {@code Collection}. The presentation
* has a specific format. It is enclosed by square brackets ("[]"). Elements
* are separated by ', ' (comma and space).
*
* @return the string representation of this {@code Collection}.
*/
@Override
public String toString() {
if (isEmpty()) {
return "[]";
}
StringBuilder buffer = new StringBuilder(size() * 16);
buffer.append('[');
Iterator<?> it = iterator();
while (it.hasNext()) {
Object next = it.next();
if (next != this) {
buffer.append(next);
} else {
buffer.append("(this Collection)");
}
if (it.hasNext()) {
buffer.append(", ");
}
}
buffer.append(']');
return buffer.toString();
}
/**
* Returns a string containing a concise, human-readable description of this
* object. Subclasses are encouraged to override this method and provide an
* implementation that takes into account the object's type and data. The
* default implementation is equivalent to the following expression:
*
See Writing a useful
* {@code toString} method
* if you intend implementing your own {@code toString} method.
*
* @return a printable representation of this object.
*/
public String toString() {
return getClass().getName() + '@' + Integer.toHexString(hashCode());
}
/**
* Returns this string.
*/
@Override
public String toString() {
return this;
}
②、StringBuilder
官方解释：以字符串的形式 返回这个builder对象的内容
/**
* Returns the contents of this builder.
*
* @return the string representation of the data in this builder.
*/
@Override
public String toString() {
/* Note: This method is required to workaround a compiler bug
* in the RI javac (at least in 1.5.0_06) that will generate a
* reference to the non-public AbstractStringBuilder if we don't
* override it here.
*/
return super.toString();
}
追溯到super.toString()实现
/**
* Returns the current String representation.
*
* @return a String containing the characters in this instance.
*/
@Override
public String toString() {
if (count == 0) {
return "";
}
return StringFactory.newStringFromChars(0, count, value);
}
③、StringBuffer
@Override
public synchronized String toString() {
return super.toString();
}
追溯到super.toString()
/**
* Returns the current String representation.
*
* @return a String containing the characters in this instance.
*/
@Override
public String toString() {
if (count == 0) {
return "";
}
return StringFactory.newStringFromChars(0, count, value);
}
public String toString() {
Iterator> i = entrySet().iterator();
if (! i.hasNext())
return "{}";
StringBuilder sb = new StringBuilder();
sb.append('{');
for (;;) {
Entry e = i.next();
K key = e.getKey();
V value = e.getValue();
sb.append(key == this ? "(this Map)" : key);
sb.append('=');
sb.append(value == this ? "(this Map)" : value);
if (! i.hasNext())
return sb.append('}').toString();
sb.append(',').append(' ');
}
}
举例：
Map map = new HashMap<>();
map.put("keyA","valueA");
map.put("keyB","valueB");
map.put("keyC","valueC");
Log.i("myinfo",map.toString());
