/*** @author Frank* @create 2017/11/24* @description*/
public class Test {public static void main(String[] args) {String src = "Hello Java Hello China";//需要处理的字符串String[] arr = src.split(" ");//按空格分割int length = arr.length;//计算数组长度StringBuilder sb = new StringBuilder(src.length());//新建一个StringBuilder对象for (int i=length-1;i>=1;i--){sb.append(arr[i]+" ");//将字符串依次加入StringBuilder中
        }sb.append(arr[0]);//最后一个单词不加空格System.out.println(sb.toString());//输出
    }
}

China Hello Java Hello

/*** @author Frank* @create 2017/11/24* @description*/
public class Test2 {public static void main(String[] args) {String src = "Hello Java,Hello China.";//需要处理的字符串StringBuilder tmp = new StringBuilder(20);//定义一个StringBuilder对象StringBuilder goal = new StringBuilder(src.length());//定义一个StringBuilder对象来存放最终要输出的信息char c;//定义一个字符变量for (int i=src.length()-1;i>=0;i--){c = src.charAt(i);//从后往前取字符if(c ==' ' || c == ',' || c == '.'){//判断是否为分隔字符goal.append(tmp);//如果是的话就把tmp加入到goal中来goal.append(c);//在把分隔字符也一起加入tmp.delete(0,tmp.length());//清空tmp}else {tmp.insert(0,c);//如果不是分隔字符，说明单词未完整，继续加入tmp中
            }}if (!tmp.equals("")){goal.append(tmp);//如果tmp中还有内容，在添加到goal中
        }System.out.println(goal.toString());//输出
    }
}

.China Hello,Java Hello

/*** @author Frank* @create 2017/11/24* @description*/
public class Test3 {public static void main(String[] args) {long time = 0;StringBuilder sb = new StringBuilder();//先生成一个比较大的字符串for (int i=0;i<10000000;i++){sb.append(i+" ");}System.out.println("字符串长度："+sb.length());//开始计算时间time = System.currentTimeMillis();StringBuilder tmp = new StringBuilder(20);//定义一个StringBuilder对象存放临时数据StringBuilder goal = new StringBuilder(sb.length());//定义一个StringBuilder对象来存放最终要输出的信息char c;//定义一个字符变量for (int i=sb.length()-1;i>=0;i--){c = sb.charAt(i);//从后往前取字符if(c ==' '){//判断是否为分隔字符goal.append(tmp);//如果是的话就把tmp加入到goal中来goal.append(c);//在把分隔字符也一起加入tmp.delete(0,tmp.length());//清空tmp}else {tmp.insert(0,c);//如果不是分隔字符，说明单词未完整，继续加入tmp中
            }}if (!tmp.equals("")){goal.append(tmp);//如果tmp中还有内容，在添加到goal中
        }System.out.println(System.currentTimeMillis()-time);//输出运行时间
    }
}

字符串长度：78888890
608

Exception in thread "main" java.lang.OutOfMemoryError: Java heap spaceat java.util.Arrays.copyOf(Arrays.java:3332)at java.lang.AbstractStringBuilder.ensureCapacityInternal(AbstractStringBuilder.java:124)at java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:448)at java.lang.StringBuilder.append(StringBuilder.java:136)at com.frank.string.test1.Test3.main(Test3.java:14)