1、概述
1.1 String：不可变字符串
public final class String implements java.io.Serializable, Comparable, CharSequence {
//final的字符数组
private final char value[];
}
1.2 StringBuilder：可改变的字符串，线程不安全
public final class StringBuilder extends AbstractStringBuilder implements java.io.Serializable, CharSequence{
//调用父类的构造器，再调用自己的append方法
public StringBuilder(String str) {
super(str.length() + 16);
append(str);
}
@Override
public StringBuilder append(Object obj) {
return append(String.valueOf(obj));
}
}
abstract class AbstractStringBuilder implements Appendable, CharSequence {
char[] value;
AbstractStringBuilder(int capacity) {
value = new char[capacity];
}
}
StringBuffer：可改变的字符串，线程安全
public final class StringBuffer extends AbstractStringBuilder implements java.io.Serializable, CharSequence{
//调用父类构造器，再调用自己的append方法
public StringBuffer(String str) {
super(str.length() + 16);
append(str);
}
@Override
public synchronized StringBuffer append(String str) {
toStringCache = null;
super.append(str);
return this;
}
}
